Question 423293
Suppose that a sample of a radioactive substance having a half-life of 11,000
 years was placed in a time capsule 1500 years ago.
 What percentage of the original sample remains today? 
:
The half life formula:
A = Ao*2^(-t/h)
where
A = amt after t years
Ao = initial amt
t = time in yrs
h = half-life of the substance
:
In this problem: 
let Ao = 100 (100%)
t = 1500 yrs
h = 11000
A = percent left after 1500 yrs
:
A = 100*2^(-1500/11000)
use a calc to find 2^(-1500/11000)
A = 100 * .90981
A = 90.98% left after 1500 yrs

:
did you understand what we did here? Any questions?