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 the left. how many boys are there in the row ?

June 27, 2026

There are 23 boys in the row.

Step-by-step explanation

Let’s decode the situation slowly:

A is 10th from the left initially.
B is 9th from the right initially.
They interchange positions.
After interchange, A becomes 15th from the left.

When A and B swap, A goes to B’s original position.
So A’s new position from the left (15th) is actually B’s original position from the left.

Now we know B’s position from:

Left: 15th
Right: 9th

For any person in a row:

Total number of boys=position from left+position from right−1\text{Total number of boys}=\text{position from left}+\text{position from right}-1Total number of boys=position from left+position from right−1

So:

Total boys=15+9−1=23\text{Total boys}=15+9-1=23Total boys=15+9−1=23

Thus, the row has 23 boys.

Mini intuition story

Imagine a line of boys where you mark one boy’s spot from both ends:

You count 15 steps from the left to reach him.
You count 9 steps from the right to reach that same boy.

If you add both counts (15 + 9), you’ve counted that boy twice , once from each side. So you subtract 1 to fix the double-count, giving you the total number of boys: 23.

Information gathered from public forums or data available on the internet and portrayed here.