Correct Answer: 12

Solution : The average of ten numbers = 24
Let's assume the sum of the ten numbers is S.
Then, according to the given information, we have:
Average = $\frac{\text{Sum of the numbers}}{\text{Total numbers}}$
= $\frac{\text{S}}{10}$ = 24
⇒ S = 240...(1)
Now, if each number is divided by 2, the new sum of the numbers would be =  $\frac{\text{S}}{2}$
So, the new average would be = $\frac{\frac{\text{S}}{2}}{10}$ = $\frac{\text{S}}{20}$
But, from equation (1), we know that S = 240.
Substituting this value in the above expression, we get:
New average = $\frac{\text{S}}{20}$ = $\frac{240}{20}$ = 12
$\therefore$ The new average of the ten numbers if each number is divided by 2 is 12.
Hence, the correct answer is 12.