Friday

November 28, 2014

November 28, 2014

Number of results: 79,401

**Calculus**

The half-life of Palladium-100 is 4 days. After 12 days a sample of Palladium-100 has been reduced to a mass of 4 mg. What was the initial mass (in mg) of the sample? What is the mass 5 weeks after the start?
*February 18, 2010 by <3*

**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*

**UIW**

Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239Np to decay to 0.100% of its original quantity
*September 19, 2013 by Anonymous*

**calculus**

The half-life of Radium-223 is 11.43 days. If a sample has a mass of 900 mg, find the mass (in mg) that remains after 5 days
*October 14, 2010 by Connor*

**calculus**

The half-life of Radium-223 is 11.43 days. If a sample has a mass of 400 mg, find the mass (in mg) that remains after 6 days
*October 14, 2014 by w*

**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*

**math**

An unknown radioactive element decays into non-radioactive substances. In 100 days the radioactivity of a sample decreases by 64 percent. a)(a) What is the half-life of the element? half-life: b)How long will it take for a sample of 100 mg to decay to 51 mg? time needed:
*May 18, 2013 by Rachel*

**chemistry**

a sample of a radioisotope had a mass of 100.0 grams. After exactly 24 days, 6.25 grams remained. The half life of the isotope is _________
*June 3, 2011 by rick*

**chemistry**

The disintegration of a radioisotope, such as I-131 to Xe-131, is another example of a first-order reaction. It has a half-life of 8.0 days. I-131 -> Xe-131 + e If you start with 1.40 g I-131, how many grams of I-131 will be left after the following days? 08 days: g, 16 ...
*July 1, 2012 by Ashley*

**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*

**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*

**Chemistry **

The metal palladium crystallizes in a face-centered cubic lattice with an edge length of 388.8 pm. What is the density of the palladium?
*February 4, 2013 by Sarah*

**chemistry**

How do you find the half-life of an element? Please explain and show me how to do this. I know the answer is 14.3 days, but I don't know how to work it. thank you! the problem is: After 42 days, a 2.0-g sample of phosphous-32 contains only 0.25g of isotope. What is the half-...
*December 13, 2007 by Ryan*

**Gen Chem**

Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239-Np to decay to 1.00% of its original quantity? I got: close to 15 days. Is this right? I figured that about 1% of the original quantity would be roughly 6.5 Half lives, and since a half ...
*March 28, 2008 by Sarah H*

**physics**

The half life of a radioactive sample is 6.93 days.after how many days will only one -tenth of the sample be left behind?
*August 1, 2012 by Mira*

**Physics 30**

The activity of a sample of a radioactive isotope is 1800Bq. If this isotope has a half-life of 16 days, what is the activity after 16 days?, 24 days?, and 60 days?
*January 9, 2011 by Matthew*

**half-life**

1. The half-life of a first-order reaction is 9.89 minutes. How many minutes will have elapsed after 27 half-lives? My answer is 267.03. 2. The half-life of a second-order reaction is 2.508 days. How many days will have elapsed after 8 half-lives? My answer is 5.330. Is this ...
*February 7, 2007 by Issac*

**chemistry**

Ba-140 has a half life of 13.0 days. What fraction of a sample will remain after 39 days?
*May 22, 2010 by Lily*

**chem**

The half-life of is 30.0 days. What fraction of a sample of this isotope will remain after 16.2 days?
*April 27, 2013 by sarah*

**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*

**Pre-Calc**

A radioactive isotope has a half life of 8.1 days. If the sample starts with 25 grams, how much will there be after 90 days?
*November 3, 2014 by Jennifer*

**earth science**

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
*November 29, 2012 by lan*

**earth science**

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
*November 29, 2012 by lan*

**earth science**

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
*November 29, 2012 by lan*

**chemistry**

Iodine-131 has a half life of eight days. What mass of iodine-131 would remain from a 20g sample after 32 days?
*September 10, 2012 by jezebel*

**chemistry**

The half-life for the radioactive decay of calcium-47 is 4.5 days.If a sample has an activity of 4.00uCi after 13.5 days, what was the initial activity of the sample?
*September 26, 2012 by Shay*

**Chemistry**

Hydrogen gas dissolves in palladium with the hydrogen molecules going into the spaces between the metal ions. Determine the molarity, molality, and percent by mass of the H2:Pd solution (d=10.8g/cm)containing 0.94g hydrogen gas dissolved in 215 grams of palladium metal.
*February 17, 2012 by James*

**Chemistry**

What is used to tell different isotopes of a particular element apart? A. the mass number B. the atomic number C. the number of protons D. the number of electrons A is the answer. After how many half-lives are there equal amounts of parent and daughter isotopes. A 1 B 2 C 3 D ...
*July 19, 2010 by Derrick*

**half-life of radioisotope**

A radioisotope has a half-life of 4 days. How much of a 20-gram sample of this radioisotope remains at the end of each time period? 1) 4 days 2) 8 days
*October 31, 2008 by Stephanie*

**Chemistry**

a)Calculate the lattice constant a in palladium (Pd).express your answer in angstroms. b) Calculate the distance (in angstroms) between adjacent (110) planes in palladium (Pd). Hint: use your work from part (a).
*November 22, 2012 by selly*

**chemistry**

the half-life of radon-222 is 3.823 days. what was the original mass if 0.050g remains after 7.646 days?
*October 21, 2010 by Anonymous*

**physics**

If the physical half-life of sulfur-35 is 87.1 days, and the biologic half-life in the testicle is 632 days, what is its effective half-life in this organ? I know i have to find the time and then the half-life. But im having trouble finding the time A(t)=Ao x e ^ (-0.693) (t...
*October 24, 2013 by Sarah*

**Chemistry**

The half-life of 131I is 8.021 days. What fraction of a sample of 131I remains after 24.063 days? 1/2 1/4 1/8 1/16 Please help. Thank you
*January 24, 2014 by Kiki*

**chemistry**

A radioactive sample contains 2.45 g of an isotope with a half-life of 3.8 days. How much of the isotope in grams will remain after 11.4 days?
*March 14, 2014 by Jacques*

**CHEM**

An isotope has a half life of 56 days. It now has 10,000DPM/ml. What will its activity be 100 days from now?
*April 17, 2013 by Jared*

**statistics**

A professional basketball player has embarked on a program to study his ability to shoot foul shots. On each day in which a game is not scheduled, he intends to shoot 100 foul shots. He maintains records over a period of 40 days of practice, with the results below. Foul Shots ...
*October 3, 2009 by MBAhopeful*

**Chemistry**

Ba-140 has a half life of 13.0 days. What fraction of a sample of Ba-140 will remain after 39 days? A. 1/8th B. 1/16th C. 1/2th D. 1/4th
*May 23, 2010 by Charleze*

**Chemistry**

The half-life of radon-222 is 3.82 days. If a sample of gas contains 4.38ug of radon-222, how much will remain in the sample after 15.2 days?
*July 19, 2010 by Leyah*

**chemistry**

A radioactive sample contains 2.45g of an isotope wiht a half life of 3.8 days. How much of the isotope in grams remains after 11.4 days? please explain
*November 26, 2011 by Monique*

**maths**

Please guide me to solve the below problem: 'A'an do 2/3 of a work in 40 days.'B'can do 1/2 of the work in 75 days.'C'can do 3/4of work in 75 days.If all them together work in how many days will they do 5/6 0f the work. I had solved the above problem like this: A can do the ...
*September 4, 2011 by Ramesh Reddy*

**Chemistry**

The half-life of iodine -131 is 16 days. If you start with 100 gram sample, how many half-lives have past when you have less than a gram left?
*October 28, 2007 by Taylor*

**physics**

The half-life of Th(227) is 18.72 days. It decays by alfa emission to Ra(223), an alfa emitter whose half-life is 11.43 days. A particular sample contains 10^6 [10E(+6)] atoms of Th(227) and no Ra(223) at time t=0. a) How many atoms of each type will be in the sample at t=15 ...
*November 6, 2014 by Mag*

**Chemistry**

Po-210 Ia an alpha emitter with a half-life of 138 days. how many grams of Po-210 remain after 552 days if the sample initially contained 5.80g of Po-210?
*October 20, 2014 by Shay*

**Chemistry**

(a) Calculate the lattice constant a in palladium (Pd). Use only the information available in the class Periodic Table, and express your answer in angstroms. (b) Calculate the distance (in angstroms) between adjacent (110) planes in palladium (Pd). Hint: use your work from ...
*November 22, 2012 by c*

**Science math**

Suppose a laboratory has a 38 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 1104 days? How much polonium is in the sample 1104 days later?
*January 7, 2013 by Joshua*

**chemistry**

The half live of Iodine-131 is 8 days. if you started out with 40 mg sample of iodine-131, then what would be the mass of the sample after 32 days? please show your work
*July 28, 2014 by Massiel*

**science**

Suppose a laboratory has a 31 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 966 days? How much polonium is in the sample 966 days later?
*March 19, 2013 by Anonymous*

**sciencemath**

Suppose a laboratory has a 31 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 966 days? How much polonium is in the sample 966 days later?
*March 19, 2013 by Anonymous*

**Radioactivity **

Beryllium-7 has a half-life of 53 D. A sample was observed for one minute and there were 26,880 decays. a.) what is the activity level of the sample? b.) what will the activity level of the sample be after 265 d? c.) after how many days will be activity level of the sample be ...
*April 17, 2014 by Samaira*

**Statistics Help Please**

The following data were collected on non-conformances for a period of 10 days. Day Sample Size Non-conformances 1 100 12 2 100 14 3 100 10 4 100 18 5 100 22 6 100 14 7 100 15 8 100 13 9 100 14 10 100 16 On what day is the proportion of non-conformances largest? smallest? What ...
*March 31, 2013 by Sue*

**physics**

After 1.84 days, the activity of a sample of an unknown type radioactive material has decreased to 85.8% of the initial activity. What is the half-life of this material? (in days)
*June 3, 2012 by andrew*

**chemistry**

Iodine-131, a beta emitter, has a half-life of 8 days.How many grams of a 10.0g sample of iodine-131 would remain after 56.0 days?
*September 26, 2012 by Shay*

**chemistry**

Iodine-131 has a half-life of 8 days. How many grams of a 12 g sample will remain at the end of 40 days? how do i solve this? i thought it was 12^40=1.5 but thats wrong...
*November 18, 2010 by jess*

**12th grade Math - word problems**

#1.) The population of bacteria after t hours is given by P(t) = 500/(1+83.33e^-0.162t) a.) What is the initial population? b.) When will the amount of bacteria in the population be 12? #2.) Which investment yields the greater amount after 4 years? a.) $900 at 9% interest ...
*September 20, 2010 by Jamie*

**Chemistry**

a) 45.02% of the sample remains after 85 days. Consider how you can use the percent of Ir-192 remaining and the number of days to calculate the mass remaining after 85 days.
*April 19, 2014 by ACDub*

**Math with science**

Radioactive iodine treatment is so successful at treating hyperthyroidism that it has virtually replaced thyroid surgery. To the nearest full day, determine how long it will take for 400 millicuries of I-131, which has a half-life of 8 days, to decay to 3.125 millicuries. 56 ...
*July 27, 2008 by Liz*

**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*

**Calculus-Modeling Equations**

An unknown radioactive element decays into non-radioactive substances. In 420 days the radioactivity of a sample decreases by 39 percent. 1.What is the half-life of the element? 2.How long will it take for a sample of 100 mg to decay to 46 mg?
*March 6, 2009 by Kim*

**chemistry **

The half life of phosphorus -32 is 14.3 days. What percentage of an original samples radioactivity remains after 57.2 days?
*May 7, 2012 by matt*

**science**

the half-life of iodine-131 is 8 days. how much iodine-131 will be left after 8 days if you have an initial mass of 1g ?
*September 28, 2007 by hamad*

**ALGEBRA**

You have 480 grams of a radioactive kind of tin. If its half-life is 10 days, how much will be left after 30 days?
*March 21, 2012 by Anonymous*

**Science Half Lives**

I am confused about how to claculate half lives. Can you explain. ( How much of a 400 gm sample od gold is left after 10.8 days if the half life is 2.7)
*January 25, 2011 by Krys*

**College Math**

In West Virginia, 100 days of the year (365)have temperatures less than32 degrees Fahrenheir. What (reduced) fraction of the days is that? I'm not sure how to go about finding the answer. Can you please help?
*July 13, 2012 by Carol*

**Math**

The population of termites and spiders in a certain house are growing exponentially. the house contains 100 termites the day you move in. After 4 days, the house contains 200 termites. Three days after moving in, there are two times as many termites as spiders. Eight days ...
*November 5, 2009 by SC*

**Chemistry**

Palladium-107 undergoes â decay (t1/2 = 6.5 x 105 yr) to form silver-107. How long will it take for 0.150 mol of silver-107 to form from 1.25 mol of palladium-107? help please...thank you :)
*December 7, 2010 by Queen*

**physics**

Suppose 32000 radioactive nuclei are in a sample. About how many remain after two days if the half-life is 22 hrs? What is the initial activity of the sample in decays per minute?
*May 5, 2009 by Anonymous*

**physics-Radioactivity**

1) The number of radioactive nuclei in a particular sample decreases over a period of 15 days to one-seventeenth the original number. What is the half-life (in days) of these nuclei? 2) What is the activity of a sample of 14C that contains 1.22E+21 nuclei?
*April 18, 2008 by Sandhya*

**Algebra**

Two different radioactive isotopes decay to 10% of their respective original amounts. Isotope A does this is 33 days, while isotope B does this in 43 days. What is the approximate difference in the half-lives of the isotopes? 3 days 10 days 13 days 33 days
*July 14, 2014 by Junior*

**Science/Chemistry**

22Na has a half-life of 951 days. How many grams of a 1.00 kg sample would be left after 4 years?
*May 16, 2011 by Samantha*

**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 *

**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 (Dr.Bob222)**

The half-life of P-32 is 14 days. How long after a sample is delivered can a laboratory wait to use a sample in an experiment if they need at least 10 percent of the original radioactivity? I need help on how to set up this problem. What is the general equation to use for a ...
*November 7, 2013 by K*

**Half-Life**

Uranium-238 decays to Lead-206. The half life of Uranium-238 is 4.5 billion years. If you have a 100 g sample. How much sample will you have after 2 half lifes?
*February 19, 2012 by Noah*

**Statistics**

A manufacturer has observed that a certain product tends to fail either very early in its life span or quite late. The engineers are interested in studying a particular product going into cellular phones. They know that the average life span of the product is 1,600 days. What ...
*March 7, 2007 by Jason L*

**3rd grade math**

erins summer vacation lasted 100 days. she kept track of the number of rainy days. it rained on 30 days. write a fraction and an equivalent fraction to show what part of all the days it rained.
*January 28, 2013 by mythreyee*

**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*

**Statistics**

According to a study by the Centers for Disease Control, the national mean hospital stay after childbirth is 2.1 days. Reviewing records at her own hospital, a hospital administrator calculates that the mean hospital stay for a random sample of 81 women after childbirth is 2.3...
*November 9, 2013 by Michael*

**math**

The mass m(t) remaining after t days from a 70 g sample of thorium-234 is given by the equation shown below. m(t) = 70e-0.0274t Find the half-life of thorium-234. (Round your answer to the nearest tenth.)
*March 13, 2010 by Anonymous*

**Chemistry**

In a 100g sample of water, determine the amount of weight that is attributed to Hydrogen and to Oxygen. i found the mass ratio which is 2:16 & then reduced its 1:8. then i set up my equation. 1x+8x=100g 9x=100g x=11.11111111 or 100/9 then i have to substitute. 1(100/9)= 11....
*January 23, 2011 by lisa*

**Chemistry**

In a 100g sample of water, determine the amount of weight that is attributed to Hydrogen and to Oxygen. i found the mass ratio which is 2:16 & then reduced its 1:8. then i set up my equation. 1x+8x=100g 9x=100g x=11.11111111 or 100/9 then i have to substitute. 1(100/9)= 11....
*January 23, 2011 by lisa*

**Math**

A 15-g sample of radioactive iodine decays in such a way that the mass remaining after t days is given by m(t) = 15e^(−0.051t), where m(t) is measured in grams. After how many days is there only 3 g remaining?
*April 22, 2013 by Zach*

**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*

**Science**

Assume that RBCs live 100 days. How many must you make per second to keep your cell count constant? You have to have the population to do this. Assume the number of RBC in the blood is P Then the rate dying is P/100 days Then the rate of regeneration must be the same. So now, ...
*January 14, 2007 by Jay*

**Chemistry**

Iodine 131 is a radioactive isotope. After 4.00 days, 70.8% of a sample of 131I remains.What is the half life of 131I?
*April 26, 2014 by Natalie*

**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*

**time n work**

a and b together can do a piece of work in16 days.b and c can do same work in 32 days.after a worked for 4 days and b for 12 days c takes it up and finishes it in 48 days.in how many days will each of them complete work
*June 24, 2014 by Navami*

**calculus -- PLEASE HELP!**

Iodine-131 is used to treat hypo-thyroidism since it is preferentially absorbed by the thyroid and typically involves a total radiation dosage of 10,000,000 millirem. Iodine-131 has a half-life of eight days. 1. Set up the appropriate integral to represent the radiation dosage...
*February 5, 2008 by anonymous*

**statistics**

A countrywide estate agency specializes in selling commercial ventures. Their records show that the mean selling time is less than 90 days. Because of recent economic conditions, they believe that the mean selling time is now greater than 90 days. A countrywide survey of 100 ...
*March 22, 2013 by general*

**7th grade**

Radon-22 has a half life of 4 days. If you begin with 32 grams of radon, how many grams will be left after 20 days?
*April 4, 2010 by Kipper*

**quantitative techniques**

a countrywide estate agency specializes i selling commercial ventures. their records show that the mean selling time is less than 90 days. because of recent economic conditions, they believe that the mean selling time is now greater than 90 days. a countrywide survey of 100 ...
*May 2, 2013 by lerato*

**economics**

1. DETROIT -- Here's a million-dollar question: How does the global economy connect American car buyers and Russian bureaucrats? One person who can answer is Reg Modlin, an emissions specialist at DaimlerChrysler AG's U.S. unit. Mr. Modlin, like many other auto-industry ...
*October 4, 2007 by Chithra*

**Chemistry**

The half-life of iodine -125 is 60 days. What fraction of iodine-125 would be left after 180 days? my teacher didnt teach us this and expects us to know it and I dont understand!!! could you explain it please!?
*October 28, 2007 by Taylor*

**Chemistry**

Which radioactive sample would contain the greatest remaining mass of the radioactive isotope after 10 years? A. 2.0 grams of 198 Au B. 2.0 grams of 42 K C. 4.0 grams of 32 P D. 4.0 grams of 60 Co By the way the numbers next to the elements are their atomic masses. thanks ...
*March 3, 2007 by Sanjay*

**Math**

I can't calculate 1 as the answer given to the following problem. I keep getting 2. Can you show me where am I going wrong? The spread of rumor among 100 people can be approximated by the equation log10(x) – log10(100-x) = (0.1)t – log10(90), where x is the number of people ...
*July 3, 2008 by Chris*

**physics**

if you have an element that starts out at 40g and has a half-life of 10 days, you keep it for 30 days- how much doe you end up with? .
*April 7, 2011 by sandy*

**Statistics**

According to a study by the Centers for Disease Control, the national mean hospital stay after childbirth is 2.1 days. Reviewing records at her own hospital, a hospital administrator calculates that the mean hospital stay for a random sample of 81 women after childbirth is 2.3...
*November 10, 2013 by Katie*

**algebra 2**

element x has a half life of 90 seconds. How much of a 100 gram sample of element x is left after half an hour
*February 15, 2011 by frances*

**finance**

if you're paying a bill for the office which has 5%, 10 days stamped across it, how much would you write a check for if you were paying a $100 bill 6 days from the date of invoice?a.$95, b.$100, c.$95, d.$105
*October 30, 2009 by demetra*

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