- #1

RRmy0440

- 10

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## Homework Statement

You have 0.0625 grams of an unstable element and 0.9375 grams of the stable daughter product. How many half-lives has it undergone？

## Homework Equations

N=No (1/2)^(t/(t1/2))

In which

N represents the final activity for a period of time

No is the original activity

t represents the time

t1/2 represents the half life

(One could also be written as

(log N/No)÷(log1/2)＝t/(t1/2)

## The Attempt at a Solution

I was rather confused about this question from the very beginning, I was wondering why is there more mass of the stable daughter product than the mass of this unstable element. Shouldn 't it always be that the daughter product have lesser mass than the element originally have, since it was undergoing a radioactive decay？

The correct answer for this question is 4 half lives.

One of my friend told me that if he add this two variables together, and states the result as real original mass of this unstable element,which turns into:

No=0.9375+0.0625=1g

Then applied the equation on the above, he then got the answer. But it does not make sense to me.

Can anyone help me with this question and explain the principle behind that please？I would be super grateful if you do that.