A and B are two heavy steel blocks. If B is placed on the top of A, the weight increases by 60%. How much weight will reduce with respect to the total weight of A and B, if B is removed from the top of A ?
- (a) 60%
- (b) 45·5%
- (c) 40%
- (d) 37·5% ✓ UPSC's answer
Why the answer is (d)
• Let A weigh 100 units. Placing B on A raises the weight by 60%, so B weighs 60 units and A + B = 160 units.
• Removing B takes away 60 units out of the combined 160.
• Reduction = 60 ÷ 160 × 100 = 37·5%, option (d).
Why the other options are wrong
- (a) 60%
- 60% is the increase relative to A alone, not the fall relative to the combined weight of A and B.
- (b) 45·5%
- 45·5% does not equal 60 ÷ 160.
- (c) 40%
- 40% does not equal 60 ÷ 160.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2019, held on 2 June 2019. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.