Question

If a couple has two boys and one girl, the probability of the next girl child to be born is

• A. $\frac{1}{4}$
• B. $\frac{1}{3}$
• C. $\frac{1}{2}$
• D. $\frac{2}{3}$
• E. $\frac{3}{4}$

Answer 1

Answer: (C)

$\frac{1}{2}$

The gametes of a female are X, X' while that of a male is X and Y.

The chances of having a girl or boy depend every time on the fusion of which two gametes from male and female.

So, the four chances are:
X (from female) X (from male) - gril (XX)

X (from female) Y from male - boy (XY)

X' (from female) X (from male) - girl (X'X)

X (from female) (Y from male) - boy (X'Y)

So, the probability of the next girl child to be born is 1/2.