UPSC Prelims 2023 · CSAT
Question 68: Basic Numeracy
There are five persons P, Q, R, S and T each one of whom has to be assigned one task. Neither P nor Q can be assigned Task-1. Task-2 must be assigned to either R or S. In how many ways can the assignment be done ?
AnswerUPSC’s answer is (d).
Task-2 goes to R or S: 2 ways. Task-1 cannot go to P or Q, and one of R and S is already used, so it goes to one of the other two among R, S, T: 2 ways. The remaining three persons take the remaining three tasks freely: 3! = 6 ways. Total = 2 x 2 x 6 = 24.
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) Wrong: the count is 2 x 2 x 6 = 24.
- (b) Wrong: the count is 2 x 2 x 6 = 24.
- (c) Wrong: the count is 2 x 2 x 6 = 24.
- (d) Right: 2 x 2 x 3! = 24.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2023, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.