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November 28, 2014

Search: A sample of a radioactive substance decayed to 93.5% of its original amount after a year. (Round your answers to two decimal places.)

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calculus
A sample of a radioactive substance decayed to 94.5% of its original amount after a year. (Round your answers to two decimal places.) (a) What is the half-life of the substance? (b) How long would it take the sample to decay to 65% of its original amount?
November 9, 2012 by kela

Calc
A sample of a radioactive substance decayed to 93.5% of its original amount after a year. a) What is the half-life of the substance? ? years (b) How long would it take the sample to decay to 10% of its original amount? ? years
November 8, 2009 by Lee

calculus
The rate at which an amount of a radioactive substance decays is modeled by the differential equation dA/dt = kA, where A is the mass in grams, t is the time in years, and k is a constant. Answer the following. a) If a 100-gram sample of the radioactive substance decays to 95 ...
March 19, 2012 by ronnieday

Science
Radioactive substance decays so that after t years, the amount remaining, expressed as a percent of the original amount, is A(t)=100(1.6)^(-t). a) Determine the function A’, which represent the rate of decay of the substance. b) what is the half-life for this substance? c) ...
March 6, 2012 by jessica

Calculus-derivatives
Verify if these are correct answers. 1. The derivative of f(x)=e^2x -e^-2x is f'(x)=2e^2x - 2e^-2x? 2.A certain radioactive substance is decaying so that at time t, measured in years, the amount of the substance, in grams, given by the function f(x)=3e^-3t. What is the rate of...
March 6, 2012 by Matthew

Math
A radioactive substance decays according to the formula Q(t) = Q0e−kt where Q(t) denotes the amount of the substance present at time t (measured in years), Q0 denotes the amount of the substance present initially, and k (a positive constant) is the decay constant. (a) ...
April 5, 2014 by Vanessa

Math
A radioactive substance decays according to the formula Q(t) = Q0e−kt where Q(t) denotes the amount of the substance present at time t (measured in years), Q0 denotes the amount of the substance present initially, and k (a positive constant) is the decay constant. (a) ...
April 6, 2014 by Vanessa

MATH!
The mass of a radioactive substance follows an exponential decay model, with a decay rate of 5% per day. A sample of this radioactive substance was taken six days ago. If the sample has a mass of 3 kg today, find the initial mass of the sample. Round your answer to two decimal...
March 15, 2012 by Kim

calculus
Carbon-14 is a radioactive substance produced in the Earth's atmosphere and then absorbed by plants and animals on the surface of the earth. It has a half-life (the time it takes for half the amount of a sample to decay) of approximately 5730 years. Using this known piece of ...
July 24, 2009 by j

Math/Calculus
After 5 days, a particular radioactive substance decays to 37% of its original amount. Find the half life of this substance. Is this right? Th= ln 2/ln(1/.37) x 5 days
October 17, 2011 by Christine

Chemistry
A radioactive sample contains 3.25 1018 atoms of a nuclide that decays at a rate of 3.4 1013 disintegrations per 26 min. (a) What percentage of the nuclide will have decayed after 159 d? % (b) How many atoms of the nuclide will remain in the sample? atoms (c) What is the half-...
April 16, 2010 by Trixie T

Chemistry
How much a 2.00 g 239 Pu would have decayed after 1.6 x 10^4 years? The half-life for 239 Pu is 2.4 x 10^4 years. amount remaining= originalamount*(.5)^(1.6/2.4) amount decayed = original - amountremaining
November 26, 2006 by James

Physics
If a sample of a radioactive isotope has a half-life of 5 year(s), how much of the original sample will be left at the end of the second year? How much will be left at the end of the third year of thr original sample? How much will be left at the end of the fourth year of the ...
November 23, 2009 by TITA

SCIENCE
We did a radioactive decay and half life lab with m&ms and I do not understand these conclusion questions: 1. how many half lives would it take for 500 nuclei to decay to 6.25% of the original number of nuclei? My ans: 3125?- do not think that's right! 2. Is there any way to ...
November 27, 2014 by Bethany

physics
If a radioactive isotope has a half-life of 1 year, how much of the original sample will be left at the end of the 2nd year?
August 23, 2012 by Anonymous

Science
if a radioactive isotope has a half-life of one year, how much of the original sample will be left at the end of the second year?
August 23, 2012 by aileen

Science
if a radioactive isotope has a half-life of one year, how much of the original sample will be left at the end of the second year?
August 23, 2012 by aileen

algebra
Two Questions: 1) A certain radioactive isotope has leaked into a small stream. 100 days later after the leak 10% of the original amount of the substance. Determine the half-life of this radioactive isotope. 2) During a research experiment, it was found that the number of ...
August 28, 2014 by kenni

Chemistry *URGENT*
URGENT help! 3. A rock sample was dated using potassium-40, Neasyrenebt ubducated tgat 1/8 of the original parent isotope is left in the rock sample. How old is the rock? 5. When a sample of lava solidfied, it contained 28g of uranium-238. It that lava sample was later found ...
March 5, 2010 by Anon

Calculus
Write a differential equation to model the situation given. Do not solve. The radioactive substance neptunium-139 decays to 73.36% of its orginal amount after 24 hours. How long would it take for 43% of the original neptunium to be present? What is the half-life of neptunium-139?
December 14, 2011 by L.S.

science
A 10g sample of radioactive substances is lift to decay for five half-lives. How much of the radioactive substance remains?
February 19, 2013 by mirian hernandez

Chemistry
Q1. The blood volume in a cancer patient was measured by injecting 5.0 mL of Na2SO4(aq) labeled with 35S (t1/2 = 87.4 d). The activity of the sample was 300 µCi. After 22 min, 12.9 mL of blood was withdrawn from the man and the activity of that sample was found to be 0.75 µCi...
April 16, 2010 by Trixie

math
A researchr assistant made 160mg of a radioactive, and found that there was only 20mg left after 45hours. a) What is the half-life of this substance? b) Write a function to represent the amount of substance left after x hours c) If the researcher kew he needed 100mg of the ...
June 23, 2013 by Kristen

Chemistry
How do you calculate the amount of a radioactive substance remaining after an integral number of half-lifes have passed?
April 6, 2010 by Tristan

algebra
Use the fact that after 5715 years a given amount of carbon 14 will have decayed to half the original amount to find the exponential decay model for carbon 14. In 1947, earthenware jars containing what was known as the Dead Sea scrolls were found by an Arab Bedouin herdsman. ...
April 12, 2014 by Kristina

Maths
A radioactive substance decays exponentially in such a way that after 50 years, 60% of the initial amount remains. Find an expression for the quantity remaining after t years.
June 15, 2014 by Rish

Math
After 150 thousand years, only 1/8 of the original amount of a particular radioactive waste will remain. The half-life of this radioactive waste is how many thousand years?
August 20, 2013 by Joy

Algebra please check my answers
1) The linear function f(x) contains the points (-10, -29) and (-2, 83). If g(x) = 25x - 50, which statement is true? A. The functions f(x) and g(x) both have positive slopes. <<< B. The functions f(x) and g(x) both have negative slopes. C. The function f(x) has a ...
May 21, 2014 by David

chemistry
a radioactive substance decays 10% in 5 days. The amount remains after 20 days?
August 15, 2014 by koteswaramma

Algebra 2 help...
A half life of a certain radioactive is 36 days. An initial amount of the material has a mass of 487 kg. Write an exponential function that models the decay of this material. Find how much radioactive material remains after 5 days. Round your answer to the nearest thousandth.
January 10, 2014 by Maria

chemistry
what fraction of an original sample of a radioactive isotope remains after three half-lives have passed? 1/8?
October 13, 2012 by jake

Science
If a 20 gram sample of a radioactive substance has a half-life of 6000 years, how many grams would be present after 18000 years?
December 5, 2012 by Owen

math
The decay of 333 mg of a radioactive substance is given by A(t) = 333e-0.024t, where t is time in years. Find the amount left after 17 years.
April 8, 2011 by allison

chemistry
A radioactive sample contains 3.25 1018 atoms of a nuclide that decays at a rate of 3.4 1013 disintegrations per 26 min. (a) What percentage of the nuclide will have decayed after 159 d? % (b) How many atoms of the nuclide will remain in the sample? atoms (c) What is the half-...
April 16, 2010 by Trixie

precalculus
Twenty percent of a radioactive substance decays in ten years. By what percent does the substance decay each year?
March 3, 2011 by katrina

Chemistry
If a 100.0 gram sample of a radioactive isotope goes through three half-lives, how much of the original radioactive isotope will remain?
January 24, 2013 by OhSnap

precal
If the half-life of a certain radioactive substance is 2000 years, estimate how many years must elapse before only 35% of the radioactive substance remains?
January 22, 2013 by james

math30
The mass of a radioactive sample is represented in the graph below. The initial mass of 32 mg decays to 8 mg after 21 hours. 1)What is the half-life of the radioactive sample, in minutes? 2)Solve each equation. a. 4 8x-1 = 8 b. 3^(2x-5) = 1/27x
July 3, 2012 by alejandro

Math-Exponential Decay
A lab technician had 58 grams of a radioactive substance. Ten days later, only 52 grams remained. Find the half-life of the radioactive substance.
May 12, 2014 by Anonymous

Calculus
The amount of carbon-14 still present in a sample after t years is given by the function where C0 is the initial amount. Estimate the age of a sample of wood discovered by an archeologist if the carbon level in the sample is only 18% of its original carbon-14 level.
March 26, 2014 by Kimberly

Physical Science- Help Please!
Suppose that you are given a 100 gram sample of a radioactive substance with a half-life of 32 days. How many grams will be left after 192 days?
December 5, 2012 by Molly

pre calculus
The age of a document is in dispute, so archaeologists test for carbon-14. Due to radioactive decay, the amount A of carbon -14 present compared to the initial amount A0 after t years is given by the formula A(t) = A0e^-0.000124t . If 72% of the original amount of carbon- 14 ...
February 8, 2014 by Raju

Math - D.E.Q.
The half-life of a radioactive isotope is the amount of time it takes for a quantity of radioactive material to decay to one-half of its original amount. i) The half-life of Carbon 14 (C-14) is 5230 years. Determine the decay-rate parameter  for C − 14.
January 18, 2011 by Justin

Physcis 30
Q1) If there are 100 radioactive atoms with a half-life of 30 seconds, how many radioactive atoms will remain after one half-life (30 seconds)? How many will remain after two half-lives (60 seconds)? Three half-lives? So basically, after 30 seconds it will be 50.After 60 sec. ...
January 6, 2011 by Marium

Chemistry
A radioactive element has a half-life of 6.41 days. What percent of the original sample will be left after 15.0 days?
January 6, 2013 by John

Science
What fraction of the original activity of a radioactive substance will remain at the end of half-life?
July 16, 2012 by Nezz

Calculus Help Please!!! URGENT!!!!
Carbon-14 has a half-life of 5700 years. In a living organism, the ratio of radioactive carbon-14 to ordinary carbon remains fairly constant during the lifetime of the organism. After the organism’s death no new carbon is integrated into the organism’s remains, so the ...
April 7, 2014 by Taylor

Chemistry
I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl 36.4% SiO2 40.9% CaCO3 ...
February 4, 2014 by Jessica

chemistry
I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl 36.4% SiO2 40.9% CaCO3 ...
February 5, 2014 by derek

chemistry
I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl 36.4% SiO2 40.9% CaCO3 ...
February 5, 2014 by derek

chemistry
I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl 36.4% SiO2 40.9% CaCO3 ...
February 5, 2014 by derek

chemistry
I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl 36.4% SiO2 40.9% CaCO3 ...
February 5, 2014 by derek

chemistry
I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl 36.4% SiO2 40.9% CaCO3 ...
February 5, 2014 by derek

calc
The half-life of polonium is 139 days, but your sample will not be useful to you after 95 % of the radioactive nuclei present on the day the sample arrives has disintegrated. For about how many days after the sample arrives will you be able to use the polonium? you want to ...
April 10, 2007 by barb

Math
In a recent dig, a human skeleton was unearthed. It was later found that the amount of 14C in it had decayed to (1/rt8) of its original amount. If 14C has a half life of 5760 years,how old was the skeleton?
August 1, 2011 by Kate

pre-calculus
Given that the radioactive decay equation is q = 1250 e-0.05t, if t is in months, the amount of milligram present after 4˝ year is?
March 4, 2012 by romain

Alegbra
Andrew measures the amount of a very unstable substance to be 100 moles. The half-life of this substance is 3 days (after 3 days, half is gone). Write an exponential function that models this situation where y is the amount of substance and x is time in days. Thank you for ...
May 1, 2012 by Jessica

maths
a man started to play a card game .in the first round he doubled the amount and he gave away a certain amount say P to his friend.In the second round,he tripled the amount left with him after the first round and gavew away an amount 2P to his friends.in the third round he ...
August 23, 2013 by arshad

Chemistry Help Please!!!
A radioactive substance has a half-life of 4 days. Suppose we have 800 mg of this substance. a) Find the equation of the mass remaining after t days. Use the exact value for k not a decimal approximation. b) Rounding your answer to the nearest tenth of a mg, find the mass ...
April 7, 2014 by Taylor

Calculus Help Please!!!
A radioactive substance has a half-life of 4 days. Suppose we have 800 mg of this substance. a) Find the equation of the mass remaining after t days. Use the exact value for k not a decimal approximation. b) Rounding your answer to the nearest tenth of a mg, find the mass ...
April 9, 2014 by Kim

algebra
Andrew measures they amount of a very unstable substance to be 100 moles. the half life of this substance is 3 days(after 3 days, half is gone). write an exponential function that models this situation where Y is the amount of substance and X is time in days. use your equation...
April 26, 2013 by Anonymous

algebra 2
In the formula A(t) = A0ekt, A is the amount of radioactive material remaining from an initial amount A0 at a given time t, and k is a negative constant determined by the nature of the material. An artifact is discovered at a certain site. If it has 72% of the carbon-14 it ...
July 13, 2011 by sky

Chemistry
Carbon-14 has a half-life of 5730 years In a plant fossil you find that the 14 C has decayed to 1/8 of the original amount how long ago was this plant
September 24, 2012 by Shay

chemistry
Carbon-14 has a half-life of 5730 . In a plant fossil, you find that the has decayed to 1/32.0 of the original amount. How long ago was this plant alive?
December 3, 2012 by niles28

Calculus
The quantity Q of radioactive carbon remaining in a 200-gram wood sample at time t is given by the expression Q(t)=200e^(−0.000225⋅t). How much radioactive carbon remains in the sample after 100500 years? I just plugged in 100500 as t and got 3.02375 grams as an ...
May 17, 2014 by Ann

Physics
Suppose a hypothetical radioactive nucleus (Hy) has a half-life of 10 days. If we have 80 gms of the substance at the start of an experiment, how many gms of the substance will remain undecayed after 30 days
May 10, 2008 by Tim

science
Please help me with this question.... The isotope caesium-137, which has a half-life of 30 years, is a product of nuclear power plants. How long will it take for the amount of this isotope in a sample of caesium to decay to one-sixteenth of its original amount? k = 0.693/t1/2...
February 5, 2007 by Mary

Science
If the half-life of a radionuclide is 1 month, is a sample of it completely decayed after 2 months?
March 22, 2013 by Dee

Pam
A 56.59 g sample of a substance is initially at 20.5 °C. After absorbing 1267 J of heat, the temperature of the substance is 116.5 °C. What is the specific heat (c) of the substance?
December 5, 2013 by Chemistry

Science- Radioactive Dating
Which of the following statements about radioactive dating is true? a. Radioactive decay is the rate at which new atoms form. b. During radioactive decay, atoms break down, releasing particles or energy. c. The rate of decay of a radioactive element cannot be approximated. d. ...
October 10, 2013 by Anonymous

algebra
Julie has 250 grams of a radioactive substance. The substance decays every hour. How long will it take until she has 20 grams of the substance left?
September 9, 2013 by Sozy

Calculus
The total worldwide box-office receipts for a long-running movie are approximated by the following function where T(x) is measured in millions of dollars and x is the number of years since the movie's release. T(x) = (120x^2)/(x^2 + 4) How fast are the total receipts changing ...
June 13, 2013 by Mike

Algebra 2
A 14 gram sample of a substance that's used to preserve fruit and vegetables has a k-value of 0.1092. Find the substance's half-life, in days. Round your answer to the nearest tenth.
May 7, 2013 by Tristan

AP Calculus
An Initial amount of 100 grams of Thorium-234 decays according to the model: dP/dt=-0.02828P (where t is measured in years). a) Find the equation for the amount of Thorium left after t years. b) Determine the half-life of this radioactive isotope c) How long will it take for ...
October 12, 2009 by RC

Math
Here is the question on compound interest. It is not graded, but is bugging me because I can't figure it out. After the third year, $2662 was in Samantha's account. If the account continues to earn 10% interest, how much money will be in the account (1)after the tenth year and...
December 19, 2007 by Chris

Chemistry
How many half lives will it take for a sample of a radioactive isotope containing 20000 radioactive nuclei to decay to 2000 radioactive nuclei
November 16, 2010 by Dianne

Algebra I
A sample of radioactive material weighing 45 grams has a decay rate of 4.25% each day. The equation y = 45(2.7)–0.0425t can be used to find the amount of material that still remains, where t is the number of days that have passed. Approximately what is the amount of material ...
March 22, 2011 by Sarah

Math-CHECK ANSWERS
hi please check these math answers! 13. If 4 out of 20 people like red jelly beans, what percent of the people do not like red jelly beans? A.5% B.20% C.80%(I PICK THIS) D.90% 14. Sally is photocopying a picture. The original picture was 4 inches wide and 6 inches long. The ...
February 10, 2014 by Tina

chemistry
2. Imagine you have two beakers. Both beakers are filled with the same amount of water. The water in both beakers is the same temperature as well. You add 50 g of Substance A to the first beaker, and 50 g of Substance B to the second beaker. After stirring both beakers, there ...
October 22, 2009 by fatima

Calculus
The amount A in grams of radioactive plutonium remaining in a 20-gram sample after t days is given by the formula A=20*(1/2)^(t/140). At what rate is the plutonium decaying when t=2 days?
November 30, 2010 by Sara

Calculus
The half-life of radioactive strontium-90 is approximately 31 years. In 1960, radioactive strontium-90 was released into the atmosphere during testing of nuclear weapons, and was absorbed into people's bones. How many years does it take until only 11 percent of the original ...
January 13, 2011 by Brittany

Math
The half-life of radioactive strontium-90 is approximately 28 years. In 1962, radioactive strontium-90 was released into the atmosphere during testing of nuclear weapons, and was absorbed into people's bones. How many years does it take until only 6 percent of the original ...
August 28, 2012 by Jason

Math
The half-life of radioactive strontium-90 is approximately 32 years. In 1961, radioactive strontium-90 was released into the atmosphere during testing of nuclear weapons, and was absorbed into people's bones. How many years does it take until only 8 percent of the original ...
September 19, 2012 by Annie

math
Phosphorus-32 (P-32) has a half-life of 14.2 days. If 200 g of this substance are present initially, find the amount Q(t) present after t days. (Round your growth constant to four decimal places.) How fast is the P-32 decaying when t = 21.5? (Round your answer to three decimal...
April 5, 2014 by Vanessa

Math
Phosphorus-32 (P-32) has a half-life of 14.2 days. If 200 g of this substance are present initially, find the amount Q(t) present after t days. (Round your growth constant to four decimal places.) How fast is the P-32 decaying when t = 21.5? (Round your answer to three decimal...
April 6, 2014 by Vanessa

math
Phosphorus-32 (P-32) has a half-life of 14.2 days. If 200 g of this substance are present initially, find the amount Q(t) present after t days. (Round your growth constant to four decimal places.) How fast is the P-32 decaying when t = 21.5? (Round your answer to three decimal...
April 7, 2014 by vanessa

Math
Phosphorus-32 (P-32) has a half-life of 14.2 days. If 200 g of this substance are present initially, find the amount Q(t) present after t days. (Round your growth constant to four decimal places.) How fast is the P-32 decaying when t = 21.5? (Round your answer to three decimal...
April 7, 2014 by Vanessa

calculus
an amount of 1000 is deposited in a bank that pays 8% interest/year compounded daily (take the number of days in a year to be 365) let an denote the total amount on deposit after n days, assuming no deposits or withdrawals are made during the period in question a. find the ...
May 20, 2012 by sofi

chemistry
a radioactive material is undergoing nuclear decay. After 40 minutes, 25% of the sample remains. What is the half-life of the sample
August 27, 2011 by marjani

Alg2
Radioactive iodine is used to determine the health of the thyroid gland. It decays according to the equation y=ae -0.0856t where t is in days. Find the half-life of this substance. Round to the tenths place.
December 6, 2011 by Rock

Alg2
Radioactive iodine is used to determine the health of the thyroid gland. It decays according to the equation y=ae -0.0856t where t is in days. Find the half-life of this substance. Round to the tenths place.
December 8, 2011 by Rock

Physics
Consider a radioactive sample with a half-life of one week. How much of the original sample will be left at the end of the second week? The third week? The fourth week?
August 29, 2013 by Tracee

advanced functions HELP!!!
Radioactive decay is the process by which an unstable element transforms into different element, typically releasing energy as it does so. For 500g of a radioactive substance with a half-life of 5.2 hours, the amount remaining is given by the formula M(t)=500(0.5) ^ t/5.2 a) ...
December 10, 2008 by james

precalc
If a savings fund pays interest at a rate of 10% per year compounded semiannually, how much money invested now will amount to $5000 after 1 year? Please round the answer to the nearest cent.
October 31, 2010 by Anna

Physics
A radioactive substance decays from 2.0kg to 1.6kg in 156 days. What is the decay constant and the half life of the substance?
August 6, 2013 by Alice

Chemistry
Suppose 1.0 mol of substance A reacts with 1.0 mol of substance B. to produce 2.0 mol of substance C. In a reaction, 2.4 mol of substance A is allowed to react with 2.1 mol of substance B. What amount in moles of substance c is produced?
April 1, 2009 by Andrew

Math
An initial amount of $2900 is invested in an account at an interest rate of 4% per year, compounded continuously. Find the amount in the account after six years. Round your answer to the nearest cent.
May 14, 2014 by Harmony

science - biology
A photosynthesis experiment uses Chlorella to track the route taken by 14C in photosynthesis. The 14C is provided from CO2 and no new sources of CO2 are available. After the experiment the scientist extracts all of the starch produced and analyses the Carbon present. She ...
May 7, 2011 by jack

math
You have just isolated a new radioactive element. If you can determine its half-life, you will win the Nobel Prize in physics. You purify a sample of 2 grams. One of your colleagues steals half of it, and eight days later you find that 0.1 gram of the radioactive material is ...
October 21, 2012 by Roseanne

Physics HELP HELP
(for some reason I keep getting this wrong. I put 90 for c, 5.6 for h and 22 for M(x), Then I took the natural log of both sides, but I keep getting it wrong) The mass of a radioactive element at time x is given by the equation below, where c is the original mass and h is the ...
November 10, 2010 by Anonymous

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