Homework Help: Math

Posted by Darwin12 on Friday, December 14, 2012 at 2:34pm.

In 10 years, 25% of a radioactive substance decays. What is its half-life?

A. 25 years
B. 24 years
C. 20 years
D. 29 years

Math - Steve, Friday, December 14, 2012 at 3:27pm
(1/2)^(10/x) = .75
x = 24
Math - Mac, Friday, December 14, 2012 at 3:34pm
You first have to find your rate

.75 = e^ (r)(10)

Then find the time for half- life

.5 = e^ (r from above)(t)
Math - Amy, Friday, December 14, 2012 at 5:16pm
Thanks

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