In a row of boys, if A who is 10th from the left and B who is 9th from the right interchange their positions, A becomes 15th from left. How many boys are there in the row?

Options

A. 23
B. 27
C. 28
D. 31

Answer

A

Explanation

Clearly, A.s new position is 15th from the left. But this is the same as B.s earlier position which is 9th from the right.