Question

A couple has $8$ children, all boys. What is the chance that their ninth child will be another boy?

• A. $1/2$
• B. $1/4$
• C. $1/8$
• D. $1/16$

Answer 1

Answer: (A)

$1/2$

Mother produces one type of gamete containing X chromosome. Father produces two types of gametes, containing X or Y chromosome. Hence, there are 1/2 chances of gamete with X chromosome mating with male gamete with X chromosome. Similarly, there are 1/2 chances of female gamete with X chromosome mating with male gamete with Y chromosome. Hence, there are 1/2 chances that their child will be a boy.

So, the correct answer is '1/2'