Two radioactive elements A and B have half-lives of 100 and 50 years respectively. Samples of A and B initially contain equal amounts/number of atoms. What is the ratio of the number of the remaining atoms of A to that of B after 200 years?

A. 4 : 1
B. 2 : 1
C. 1 : 1
D. 1 : 2
E. 1 : 4

Correct Answer: Option A

A. 4 : 1

Explanation
N – T N/2 = 100 N/4 = 200

N – T N/2 = 50 N/4 = 100 N/8 = 150 N/16 = 200

Ratio: N/4 N/16 => 16/4 = 4 : 1