In a row of boys P is 13th from the left. Q is 19th from the right and 21st from the left. How many boys are there towards right of P?

26

First of all, we have to find the total number of boys in the row,

T = L + R - 1

= 21 + 19 – 1

⇒ 39

As the total number boys are 39 in the row and P is 13th from the left, therefore there will be 26 boys towards right of P.