# Question #1dc8f

##### 1 Answer

It is four.

#### Explanation:

The half life of any substance is given by:

Hence

We want to find:

Substituting the previous equations into the above gives

**[equation A]**

For a sample of N atoms, the activity, A, is given by:

Where

So for sample 1: **[equation 1]**

and for sample 2: **[equation 2]**

We are told that that

and also

Substituting both of these into equation 2 we get:

So

**[equation 3]**

Comparing equation 1 and 3 we can see that:

and so

Hence the ratio of halve lives is 4 (by comparing this result to equation A)