# If 1/8 of an original sample of krypton-74 remains unchanged atter 34.5 minutes, what is the half life of krypton-74?

##### 1 Answer

May 24, 2017

11.5 minutes (11 minutes, 30 seconds)

#### Explanation:

this is a nice easy half-life calculation as no equation is required.

if you see one over two the power of n

you start off with 1 multiple of the sample (the entire sample).

after 1 half life, you are left with half of the sample (

after 2 half lives, you are left with a quarter of the sample (

after 3 half lives, you are left with an eighth of the sample (

therefore 3 half lives have occured to give

34.5 minutes divided by 3 is 11.5

so the half-life of

=)