Question

Plutonium-236 is an alpha emitter with a half-life of 2.86 years. how long will it take for the 1.10 mg sample of pu−236 to decay to 0.140 mg ?

Answer 1

1.1 / 2 = .7 --> 2.86 yrs

.7 / 2 = .45 —> 5.72 yrs

.45 / 2 = .225 —> 8.58 yrs

.225 / 2 = .1125 —> 11.44 yrs

So, for the sample of plutonium to reach .140 mg it should take a little less than 11.44 years.

Hope this helps