Question

The half life of a radioactive kind of cesium is 30 years. How much will be left after 120 years, if you start with 960 grams of it

Answer 1

60 grams

Explanation:

120 years / half-life of 30 years = it will grow half the size 4 times

960 * 1/2 ^ 4 = 960 * 1/2 * 1/2 * 1/2 * 1/2 = 60 grams