2013 CSAT, all questions
UPSC Prelims 2013 · CSAT
Question 61: Basic Numeracy
A gardener has 1000 plants. He wants to plant them in such a way that the number of rows and the number of columns remains the same. What is the minimum number of plants that he needs more for this purpose ?
a14
b24
c32
d34
AnswerUPSC’s answer is (b).
Equal rows and columns means the plants must fill a perfect square. 31 x 31 = 961 is too few for 1000 plants, and 32 x 32 = 1024 is the first square above 1000. So the gardener needs 1024 - 1000 = 24 more plants. Know your squares near 1000: 31 squared is 961 and 32 squared is 1024.
Why each option is right or wrong
- (a) Wrong. 1000 + 14 = 1014, which is not a perfect square.
- (b) Right. 1000 + 24 = 1024 = 32 x 32.
- (c) Wrong. 1000 + 32 = 1032, which is not a perfect square.
- (d) Wrong. 1000 + 34 = 1034, which is not a perfect square.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.