UPSC Prelims 2020 · CSAT
Question 37: Basic Numeracy
How many integers are there between 1 and 100 which have 4 as a digit but are not divisible by 4?
AnswerUPSC’s answer is (c).
Numbers up to 100 with the digit 4: 4, 14, 24, 34, 54, 64, 74, 84, 94 (units digit 4) and 40 to 49, together 19 numbers. A number is divisible by 4 if its last two digits are; of these, 4, 24, 40, 44, 48, 64 and 84 are divisible, seven numbers. 19 - 7 = 12.
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) 5 is far below the correct count.
- (b) 11 misses one number.
- (c) Right: 19 numbers have a 4, and 7 are divisible by 4.
- (d) 13 overcounts by one.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.