# Math Help - radioactive substance problem

a radioactive substance has a half life of 20 days.

i) how much time is required so that only 1/32 of the original amount remains? i can figure out it would take 5 half lives but i don't know how to show it mathematically

ii) find the rate of decay at this time.

2. Use the equation:

$A_o = A 2^{t / t_{\frac{1}{2}}}$

?

A_o is the initial amount of matter
A is the final amount of matter
t is the time it takes to decay
t_(1/2) is the half life.