Given TA = 1 hour and TB = 2 hours , At t = 0 number of atoms of A = number of atoms of B = N0 ∴ Number of atoms of A after 2 hours (i.e. after 2 half lives of A) is NA = N0(
1
2
)2 =
N0
4
Number of atoms of B after 2 hrs (i.e. after 1 half life of B) is NB =