Homework Help: Math

Posted by Annie on Wednesday, September 19, 2012 at 3:46pm.

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 amount absorbed remains?

Math - Steve, Wednesday, September 19, 2012 at 4:43pm
Since 1/8 = (1/2)^3, it will take 3 half-lives, or 96 years.
Math - Reiny, Wednesday, September 19, 2012 at 5:03pm
I would say
.08 = (1/2)^(t/32)
ln .08 = (t/32) ln .5
t/32 = ln .08/ln .5 = 3.6438..
t = 116.6 years

rough check:
after 32 years --- 50% left
after 64 years --- 25% left
after 96 years --- 12.5% left , (which is 1/8 but not 8%)
after about 16 more years we would lose about 1/4 of what was left, leaving appr 3/4 of 12.5 or appr 9%

answer is quite plausible
math - oops - Steve, Wednesday, September 19, 2012 at 5:34pm
ouch. How did I read 8% as 1/8?

As usual, go with Reiny's answer!

Answer this Question

Related Questions

Math - The half-life of radioactive strontium-90 is approximately 28 years. In ...
Calculus - The half-life of radioactive strontium-90 is approximately 31 years. ...
Calculus - [Exponential growth & decay] The half-life of radioactive ...
Calculas - In the early 1960s, radioactive strontium-90 was released during ...
calculus - In the early 1960s, radioactive strontium-90 was released during ...
AP Environmental Science (URGENT) - Strontium-90 is a radioactive waste product ...
Chemistry - The half-life for beta decay of strontium-90 is 28.8 years. A milk ...
chemistry - Strontium-90 decays through the emission of beta particles. It has ...
chemistry - Strontium-90 has half-life of 28 years. if a 1.00-mg sample was ...
Math - The half-life of strontium-90 is 28 years. How long will it take a 60 mg ...

For Further Reading

First Name:
School Subject:
Answer: