One of the waste byproducts of a nuclear reactor using uranium-235 is strontium-90 with half-life of about 28 years. If we have 100 pounds of this radioactive waste:

(a) 140 years

(b) 3.125 pounds

Explanation:

QuestIons

(a) How long is five half-life

(b)  How much radioactive strontium is left after five half-life

Given that:

Half-life is about 28 years; &

There are 100 pounds of this radioactive waste

Five half-life will be;

= 28 × 5

= 140 years

The amount of radioactive remaining after five half-life is:

= 100 × 0.03125

= 3.125 pounds

the answer is a and have a great day