UPSC Prelims 2018 · CSAT
Question 68: Basic Numeracy
A lift has the capacity of 18 adults or 30 children. How many children can board the lift with 12 adults?
AnswerUPSC’s answer is (b).
The lift's capacity is fixed, so 18 adults take the same space as 30 children: one adult equals 30/18 = 5/3 children. Twelve adults take 12 × 5/3 = 20 children's worth of space. The remaining space is 30 - 20 = 10 children. Another way: 12 of 18 adults fills 2/3 of the lift, leaving 1/3 of 30 children, which is 10.
How you could have got this
No shortcut here: in a “how many” question, ruling out options doesn’t help. Every statement has to be judged.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) 6 children would leave part of the lift empty.
- (b) Correct: 30 - 20 = 10 children.
- (c) 12 children plus 12 adults equals 32 children's space, over 30.
- (d) 15 children plus 12 adults equals 35 children's space, over 30.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2018, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.