Suppose there are 2 x 107 Radon atoms trapped in a basement. Radon has a half life of t1/2 = 3.83 days. 

Estimate the number of radon atoms will be left after 23 days.

N = atoms

Initially, the Radon is decaying at a rate of 63 disintegrations/second. Estimate the decay rate after 23 days

R =  disintegrations/second