# You have 100g of radioactive plutonium-239 with a half-life of 24,000 years. how much will remain after (a) 12,000 years, (b) 24,000 years, and (c) 96,000 years?

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also, can you explain the answer and how you solved to get that. thanks

also, can you explain the answer and how you solved to get that. thanks

##### 1 Answer

(a)

(b)

(c)

#### Explanation:

A half life is the number of years it takes for a radioactive substance to decay to half its original mass or weight.

So for radioactive plutonium-239 with a half-life of 24,000 years, it will take 24,000 years to decay to 1/2 its weight so

In 12,000 years, it has only had time to decay

That means it has decayed only

96,000 years is equal to

At half-life time 0 we have 100g

At half-life time 1 we have 50g

At half-life time 2 we have 25g

At half-life time 3 we have 12.5g

At half-life time 4 we have 6.25g

At half-life time 5 we have 3.125g

At half-life time 6 we have 1.625g

There is a formula, but this tells you how to figure it out.