If P = +, Q = −, R = ×, S = ÷, then insert the proper notations between the successive numbers in the equation 60_15_3_20_4 = 20:
Answer & explanation
Answer: (b) QRPS
Replacing the letters as in (b) gives 60 − 15 × 3 + 20 ÷ 4 = 60 − 45 + 5 = 20. The other orders give 60, 61.75 and −73.
- Test each option, doing ÷ and × before + and − (BODMAS).
- (a) SPRQ: 60 ÷ 15 + 3 × 20 − 4 = 4 + 60 − 4 = 60.
- (b) QRPS: 60 − 15 × 3 + 20 ÷ 4 = 60 − 45 + 5 = 20, which matches.
- (c) QRSP: 60 − 15 × 3 ÷ 20 + 4 = 60 − 2.25 + 4 = 61.75.
- (d) SPQR: 60 ÷ 15 + 3 − 20 × 4 = 4 + 3 − 80 = −73.
Remember · In symbol-substitution items, test each option with BODMAS; a rough size check quickly rules out most options.
Question and answer: UPSC's official GS Paper II (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·