Refer the below table and answer the question that follows. Discipline → Boys | Girls Engineering — 120 | 80 Medical — 80 | 120 What percentage of students who chose medical are boys?

Correct — A. The base is the medical row, not the whole table.

Medical students = boys + girls
= 80 + 120 = 200

Boys among them = 80

Required percentage = (80 ⁄ 200) × 100
= 0.4 × 100 = 40% → option (a).

Why the others are wrong

• (b)
  50% — 50% is boys as a share of everybody — 120 + 80 = 200 boys out of 400 students. That answers a different question from the one printed.
• (c)
  45% — 45% would need 90 boys among the 200 medical students. The table prints 80, and 80 ⁄ 200 is 40%.
• (d)
  30% — 30% is 120⁄400, the medical girls as a share of all four hundred students. The stem asks for boys, and it asks within the medical row.

A percentage is meaningless until its base is named. The phrase 'percentage of students who chose medical' fixes the base as the medical total, and the table never prints that total — you build it as 80 + 120 = 200.

The grand total of 400 sits in plain sight as a rival base, and so does the engineering row.

The table is symmetric: engineering runs 120 boys and 80 girls, medical runs the mirror image, so overall there are 200 boys and 200 girls.

Key facts

• The medical row holds 80 boys and 120 girls, a total of 200 students.
• 80 out of 200 is 40%.
• The table holds 400 students in all, 200 boys and 200 girls.

Common traps

• Using the grand total of 400 as the base, which turns 80 into 20%
• Answering with all the boys in the table, 200 of 400, which is 50%
• Reading the engineering row, where boys are 120 of 200 or 60%

No directly related past PYQ was found.