UPSC Prelims 2021 · CSAT
Question 35: Basic Numeracy
In a group of 120 persons, 80 are Indians and rest are foreigners. Further, 70 persons in the group can speak English. The number of Indians who can speak English is
AnswerUPSC’s answer is (d).
There are 120 persons: 80 Indians and 40 foreigners. Of the 70 English speakers, at most 40 can be foreigners, since only 40 foreigners exist. So at least 70 − 40 = 30 English speakers are Indians. The number could be larger if fewer foreigners speak English, up to 70, which is below 80 Indians. The number of Indians who speak English is therefore 30 or more. Remember: for minimum and maximum counts, push one group to its limit and see what remains.
Why each option is right or wrong
- (a) 20 is below the minimum of 30.
- (b) 30 is only the least possible value; more Indians could speak English.
- (c) 30 is a minimum, not a maximum, so 'or less' is wrong.
- (d) Right: at least 30 Indians speak English, since at most 40 of the 70 are foreigners.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.