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UPSC CSE CSAT 2019 · Question 34 · Arithmetic: percentage, ratio, averages, time & work

In an examination, A has scored 20 marks more than B. If B has scored 5% less marks than A, how…

CSAT 2019 · Q34

Arithmetic: percentage, ratio, averages, time & work Easy

In an examination, A has scored 20 marks more than B. If B has scored 5% less marks than A, how much has B scored?

Answer & explanation

Answer: (b) 380

B's shortfall of 5% is measured on A's marks and equals the 20-mark gap, so A has 400 and B 380.

  1. B = A − 20, and B = 95% of A.
  2. So 5% of A = 20, giving A = 400.
  3. B = 400 − 20 = 380.
  4. Check: 95% of 400 = 380.

Remember · When a percentage gap equals a known difference, that difference is the percentage of the base.

Question and answer: UPSC's official GS Paper II (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·

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