For an unknown sample of the experiment, students measure 1602 counts when they first receive their sample and 1317 counts 3.5 minutes later. Calculate the half-life t12 of their sample.

Answer 1

If t12 is the half life in minutes,
1317 = 1602*2^-(3.5/t12)

Solve for t12

2^-(3.5/t12) = 0.8221
3.5/t12 = .2826
t12 = 12.4 minutes