Question

A radioactive material has a half life of 10 years. What is the fraction of the initial isotope is left after 60 years

Answer 1

0.015625 left.

Explanation:

If we start with say 100g of the material, in 10 years there is 100 * 1/2 =

50g left ( = 0.5 left).

In 20 years there is 100*(1/2)^2 = 25 g left.

In n*10 years there is 100(1/2)^2 g

So in 60 years there is 100(1/2)^6 = 1.5625 g left

This is 1.5625 %

= 0.015625 of the origin material left.

Answer 2

1/64

Explanation:

10 = ½

20 = ¼

30 = ⅛

40 = 1/16

50 = 1/32

60 = 1/64