Question

Iodine-131 has a half life of about 8 days. About how much is left from a 100 gram sample after 16 days?

Answer 1

25 grams.
When dealing with half lifes use the formula \[y = Ce ^{t/h}\]
C is the starting amount, in this case 100 grams, h is half life time or 8 days and t is the amount of time passed or 16 days.
so plugging everything in we get
\[y=100*(1/2)^{16/8} = 100*(1/2)^2 = 100*1/4\] = 25 grams

Answer 2

i ment to say \[y = C(1/2)^{t/h}\]