Science
posted by Korina on .
If a radioactive isotope has half life of 5 days,how long will it take for its radioactive strength to be a maximum of one thousandth,(1/1000) of its original value?
Can anyone give me a VERY SIMPLE explanation of this please?
Thank you.

Solve this equation for the number of days, x:
(0.5)^(x/5) = 1/1000
You can compute x by taking the log of both sides.
x/5 = 9.97
x = 49 days
The words "a maximum of" are not needed in your question. After 49 days, the radioactive strength will be exactly 1/1000 of the original value, except for roundingoff error. You only have one significant figure in the halflife.