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WBCS Main Examination 2023 — Paper VI: Arithmetic and Test of Reasoning · Question 42 of 200

Q42
ArithmeticAverages & Ages
The average weight of 30 students of a class is 45 kg. The average weight of girls is 37kg. and that of boys is 49 kg. Find the number of boys in the class.
  1. a.10
  2. b.15
  3. c.20
  4. d.22

Answer: (C) 20

Total weight = 30 × 45 = 1350 kg. With b boys, 49b + 37(30 − b) = 1350, so 12b = 240 and b = 20. 10 is the number of girls, the most tempting wrong answer.

Q41 Whole paperQ43
The average weight of 30 students of a class is 45 kg. The average … — WBCS Main Examination 2023 Q42 | Prostuti360°