3/5 of all married couples have more than one child. 2/5 of all married couples have more than 3 children. What fraction of all married couples have 2 or 3 children? Choose the correct choice from the following options:
A) 1 / 5
B) 1 / 4
C) 7 / 20
D) 3 / 5
E) it can not be determined from the given information .

Rationale: plug in simple numbers . take 100 couples for example . 3 / 5 of 100 couples have more than one child = 60 couples . 2 / 5 of 100 couples have more than 3 kids = 40 couples . this implies that 40 couples are a subset of 60 couples and the complement of 60 couples within those 100 couples , which equals 20 couples have either one or no kids at all . we need to find couples that have 2 or 3 kids , so essentially , it is 60 - 40 = 20 . fraction will be 20 / 100 = 1 / 5 . option a
Answer: A