Question

Ram is visiting a friend. Ram knows that his friend has $2$ children and $1$ of them if a boy. Assuming that a child is equally likely to be a boy or girl, then the probability that the other child is girl, is

• A. $1/2$
• B. $1/3$
• C. $2/3$
• D. $7/10$

Answer 1

Answer: (C)

$2/3$

If a family has 2 children, the sample space can be reprsented as S = {(b,b), (b,g), (g,b), (g,g)}. Thus the total number of outcomes is 4.

Given 1 of them is boy, hence the possible outcomes are {(b, b), (b, g), (g, b)} = 3

Out of these the total number of outcomes for the event that one is boy and other is girl = 2

Hence, the probability that the other child is a girl, is $\frac{2}{3}$