UPSC Prelims 2022 · CSAT
Question 45: Basic Numeracy
Five friends P, Q, X, Y and Z purchased some notebooks. The relevant information is given below :
- 1.Z purchased 8 notebooks more than X did.
- 2.P and Q together purchased 21 notebooks.
- 3.Q purchased 5 notebooks less than P did.
- 4.X and Y together purchased 28 notebooks.
- 5.P purchased 5 notebooks more than X did.
If each notebook is priced ₹40, then what is the total cost of all the notebooks?
AnswerUPSC’s answer is (a).
Let X have x notebooks. From item 5, P = x + 5; from item 3, Q = P − 5 = x; from item 2, P + Q = 2x + 5 = 21, so x = 8. Then X = 8, P = 13, Q = 8, Z = x + 8 = 16 (item 1), and from item 4, Y = 28 − 8 = 20. Total = 8 + 13 + 8 + 16 + 20 = 65 notebooks, and at ₹40 each the cost is 65 × 40 = ₹2,600. Check against the items: P + Q = 21, Z − X = 8, X + Y = 28 and P − X = 5 all hold.
Why each option is right or wrong
- (a) Correct: 65 notebooks at ₹40 each.
- (b) ₹2,400 is 60 notebooks, but the count is 65.
- (c) ₹2,360 is 59 notebooks.
- (d) ₹2,320 is 58 notebooks.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2022, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.