UPSC PYQPrelims 2026

Civil Services Examination · प्रश्न 79

There are two chemicals which do not react with each other. A container contains 10 litres of the chemical A. One litre of this chemical is removed from it and one litre of the chemical B is poured. Then one litre of the mixture is removed from the container and one litre of B is poured. If this process of replacing one litre of the mixture by one litre of B is performed once more, then what is the volume of B that is present in the container approximately (in percentage)?

  1. 25
  2. 27
  3. 29
  4. 31
उत्तर देखें और व्याख्या

उत्तर: (B) 27

व्याख्या

After three replacements, A left = 10 × (9/10)³ = 7.29 L, so B = 2.71 L ≈ 27%.