# The half-life of Iodine-131 is approximately 8 days. What is the amount of Iodine-131 left from a 35 gram sample after 32 days?

Apr 2, 2018

$2.2$ grams

#### Explanation:

32 days means 4 half lives since one half life is 8 days.
That means it will be halved 4 times... so the ratio between the initial amount and the amount after 32 days will be ${0.5}^{4}$.

$35 \times {0.5}^{4} = 2.1875$

There will be $2.2$ grams left.