2019 CSAT, all questions

UPSC Prelims 2019 · CSAT

Question 37: Basic Numeracy

If x is greater than or equal to 25 and y is less than or equal to 40, then which one of the following is always correct ?

ax is greater than y
b(y – x) is greater than 15
c(y – x) is less than or equal to 15
d(x + y) is greater than or equal to 65

AnswerUPSC’s answer is (c).

Here x is at least 25 and y is at most 40. The largest possible value of y - x is 40 - 25 = 15, reached when y is as big and x as small as allowed. So y - x is always 15 or less. Test the others with extreme values: x = 25, y = 40 shows x need not exceed y, and y very small makes x + y fall below 65.

Why each option is right or wrong
  • (a) Wrong: x = 25, y = 40 gives x less than y.
  • (b) Wrong: y - x never exceeds 15.
  • (c) Right: the maximum of y - x is 15.
  • (d) Wrong: y = 0, x = 25 gives a sum of 25.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

Practise this paper timedPrevious questionNext question

Source: UPSC, Civil Services (Preliminary) Examination 2019, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.