In a row of 60 students, Meena is 25th from the left and Rupa is 20th from the right. How many students are there between them?

Correct — D.
Rule: count both ranks from the same end, subtract, then take away 1.

Rupa from the left = 60 − 20 + 1 = 41st
Meena from the left = 25th
Students between = 41 − 25 − 1 = 15 → option (d).

Why the others are wrong

• (a)
  11 — 11 between them would put Rupa 25 + 11 + 1 = 37th from the left, which is 24th from the right, not 20th.
• (b)
  10 — 10 between them would put Rupa 36th from the left, which is 25th from the right. The question places her 20th.
• (c)
  12 — 12 between them would put Rupa 38th from the left, which is 23rd from the right, three places off her given rank.

In a row, a person's rank from the left and rank from the right add up to total + 1. So Rupa, 20th from the right in a row of 60, is 60 − 20 + 1 = 41st from the left.

Once both ranks count from the same end, the people strictly between them number larger rank − smaller rank − 1: here 41 − 25 − 1 = 15.

Key facts

• Rank from the left + rank from the right = total + 1.
• People between two ranks counted from the same end = larger rank − smaller rank − 1.
• When left rank + right rank does not exceed the total, people between = total − (left rank + right rank).

Common traps

• Dropping the + 1 when converting 20th from the right, which gives 40 instead of 41
• Subtracting the ranks without taking away 1 (41 − 25 = 16), which counts Rupa herself

No directly related past PYQ was found.