UPSC Prelims 2014 · CSAT
Question 19: Basic Numeracy
There are 50 students admitted to a nursery class. Some students can speak only English and some can speak only Hindi. 10 students can speak both English and Hindi. If the number of students who can speak English is 21, then how many students can speak Hindi, how many can speak only Hindi and how many can speak only English ?
AnswerUPSC’s answer is (d).
Everyone speaks at least one language, so English-only + Hindi-only + both = 50. English-only = 21 - 10 = 11. Hindi-only = 50 - 21 = 29, the students outside the English group. Total Hindi speakers = 29 + 10 = 39. So the answer is 39, 29 and 11. Draw two overlapping circles and fill the overlap first; the rest follows.
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) English-only 29 plus the 10 who speak both would make 39 English speakers, not 21.
- (b) English-only 22 plus the 10 who speak both would make 32 English speakers, not 21.
- (c) English-only 13 plus the 10 who speak both would make 23 English speakers, not 21.
- (d) Right. 39 Hindi speakers, 29 Hindi-only, 11 English-only.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2014, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.