Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and the Yahoo Answers website is now in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
The half-life of radium-226 is 1600 yrs. old?
Okay so I'm having trouble with this decay problem in my precalculus class.
2. The half-life of radium-226 is 1600 years. Suppose we have a 22-mg sample.
A.) Find a function that models the mass remaining after t years.
B.) How much of the sample will remain after 4000 years?
C.) After how long will only 18mg of sample remain? Round your answer to the nearest year.
Im just having a ton of trouble with these. We have been working with uninhibited radioactive decay.
A(t)= Asub0e^kt k<0
2 Answers
- Mike GLv 78 years agoFavorite Answer
Using the half life formula
A) A = 22*(0.5)^(t/1600)
B) A = 22*(0.5)^(4000/1600) = 3.89 mg
C) 18 = 22(0.5)^(t/1600)
log (18/22) = (t/1600)log 0.5
t = 463 years
Using the exponential decay formula
A) 0.5 = e^1600k
1600k = ln 0.5
k = -0.0004332
A = 22e^(-0.0004332t)
B) A = 22e^-1.732 = 3.89 mg
C) 18 = 22e^(-0.0004332t)
-0.0004332t = ln(18/22)
t = 463 years
- 5 years ago
totally wrong ^^^
For half-life its actually:
A) 22*(2)^(-t/1600)
still working on the rest
