Wednesday

July 30, 2014

July 30, 2014

Number of results: 44,011

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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**

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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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*

**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 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*

**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*

**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*

**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*

**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*

**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*

**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*

**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**

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*

**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*

**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? PLEASE HELP!!!!
*July 1, 2012 by Ashley*

**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*

**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 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*

**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*

**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*

**adult education**

Given Data: Total Sales: $912,500 % of customers that take discounts: 40% % of customers that do not take discounts: 60% # of days that cusomers who take discounts pay by: 10 Days # of days that customers who do not take discounts pay by: 40 Days # of days that customers who ...
*November 15, 2010 by Brandye O'Conner*

**Math**

Ansgar is writing a novel. He writes seven days a week. On each of those days he write for at least 4 hours but never more than 8 hours. Last week, he wrote for exactly 46 hours. What is the maximum number of days on which he could have written for 8 hours? A. 2 days B. 3 days...
*June 6, 2014 by Anonymous*

**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*

**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**

If there is a radiation that has a half life of 10 days and we have it for 110 days, what will be the fraction of radiation left?
*July 10, 2011 by g*

**Chemistry**

If there is a radiation that has a half life of 10 days and we have it for 110 days, what will be the fraction of radiation left?
*November 6, 2011 by Jennifer*

**CALC -- integrals!**

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 4, 2008 by anonymous*

**math**

of the following which is the closest approximation to the amount of time it takes to read a 487-page book at the rate of 25 pages a day ? a. 20 days b.25 days c.15 days d.10 days e.30 days
*February 27, 2011 by nylija*

**chemistry**

If I 131 has a half-life of 8 days, what fraction will be left after a year?
*July 7, 2011 by g*

**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*

**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*

**college**

. S-35 (t1/2 = 87.4 d) is used in cancer research. The biological half-life in the human body is 90 days. What is the effective half-life of S-35?
*May 3, 2010 by kurt*

**Chemistry**

32P is a radioactive isotope with a half-life of 14.3 days. If you currently have 48.1 g of 32P, how much 32P was present 3.00 days ago?
*June 10, 2012 by Anonymous*

**college chem**

S-35 (t1/2 = 87.4 d) is used in cancer research. The biological half-life in the human body is 90 days. What is the effective half-life of S-35?
*May 3, 2010 by Anonymous*

**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*

**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 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**

Iodine-131 is used to destroy thyroid tissue in the treatment of an overactive thyroid. the half-life of iodine-131 is 8.02 days. if a hospital recieves a shipment of 200.0g of iodine-131, how much iodine-131 would remain after 32 days?
*December 8, 2010 by monique n*

**Chemistry**

Compute the volume of helium at 1.0 atm and 298 K that will be collected if 2.5 g of 222Rn is stored in a container able to expand to maintain a constant pressure for 15 days. Assume that 222Rn decays to 218Po with a half-life of 3.824 days.
*December 11, 2012 by Sandy*

**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*

**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**

If Sam can do a job in 4 days that Lisa can do in 6 days and Tom can do in 2 days, how long would the job take if Sam, Lisa, and Tom worked together to complete it? A. 0.8 days B. 1.09 days C. 1.23 days D. 1.65 days E. 1.97 days thanks.
*January 6, 2009 by tammy*

**math**

Sam can do a job in 4 days that Lisa can do in 6 days and Tom can do in 2 days, how long would the job take if Sam, Lisa, and Tom worked together to complete it? A. 0.8 days B. 1.09 days C. 1.23 days D. 1.65 days E. 1.97 days thanks.
*January 7, 2009 by tammy*

**Chemistry**

The half-life of phosphorus-32 is 14.26 days. The decay constant is k=4.86×10−2/days. If you accidentally spill phosphorus-32 onto your shoe, how long would it take before 99.9% of the radioactive material has decayed so that you can safely wear the shoes again?
*May 1, 2011 by Anonymous*

**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*

**MAT 201**

The number of vacation days taken by employees of a company is normally distributed with a mean of 14 days and a standard deviation of 3 days. For the next employee, what is the probability that the number of days of vacation taken is less than 10 days? More than 21 days?
*May 15, 2014 by bob*

**statistics**

The number of vacation days taken by employees of a company is normally distributed with a mean of 14 days and a standard deviation of 3 days. For the next employee, what is the probability that the number of days of vacation taken is less than 10 days? More than 21 days?
*May 15, 2014 by bob*

**possessive nouns**

Soldiers carried several ___ cold rations. Is it A. days B day's C.days' D. days's My answer is c. days'
*November 2, 2009 by shawn*

**English**

Soldiers carried several days cold nations. should days chage to a possessive noun from days to days'
*November 10, 2011 by Chris*

**Algebra**

During the last 365 days it was sunny 5 days less than 4 times the number of rainy days. How many days did it rain?
*September 7, 2010 by Alicia*

**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*

**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*

**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*

**General chemistry**

A researcher needs 5.00 mg of 128Ba for an experiment. If the half-life of 128Ba is 2.43 days, how many milligrams of 128BaCl2 must she order from the manufacturer if it takes 4.50 days to ship the material from the manufacturer to the university? (Assume the molar mass of ...
*April 27, 2010 by me*

**chemistry**

Mercury-197 is used for kidney scans and has a half-life of 3 days. if the amount of mercury-197 needed for a study is 1.0 grams and the time allowed for shipment is 15 days, how much mercury-197 will need to be ordered.
*December 8, 2010 by monique n*

**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*

**senior problem solving**

a colony of ants doubles every 20 days. if the colony has 350 ants today, how many are/were present in 50 days? a. in 50 days? b. 55 days ago? c. in 30 days?
*March 27, 2014 by dareus boddie*

**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*

**Healthcare Statistic**

The difference between inpatient service days and discharge days is that service days are compiled while the patient is hospitalized and discharge days are compiled after the patient has been discharged from the hospital. T/F
*December 16, 2013 by Anonymous*

**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*

**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*

**Environmental Science**

A nuclear burning power plant produces a total power of 1.1kW. It serves a community that requires 2.85 x 107 kJ of power over the entire year. How many days per year does the power plant need to operate to provide all this power? 300 days 250 days 365 days 200 days 150 days
*December 22, 2013 by Kayla*

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