UPSC Prelims 2022 · CSAT

Question 26: Basic Numeracy

On one side of a 1·01 km long road, 101 plants are planted at equal distance from each other. What is the total distance between 5 consecutive plants?

a40 m

b40·4 m

c50 m

d50·5 m

AnswerUPSC’s answer is (b).

101 plants at equal spacing along 1010 m (1.01 km), with plants at both ends, make 100 gaps, each 1010 ÷ 100 = 10.1 m. Five consecutive plants span 4 gaps: 4 × 10.1 = 40.4 m. Count gaps, not plants; a common slip is to multiply the spacing by 5. With n plants in a line there are n − 1 gaps, so 5 plants always span 4 gaps.

Why each option is right or wrong

(a) 40 m uses a gap of 10 m.
(b) Correct: 4 gaps of 10.1 m = 40.4 m.
(c) 50 m uses 5 gaps of 10 m.
(d) 50.5 m uses 5 gaps of 10.1 m, but five plants have only 4 gaps.

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

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Source: UPSC, Civil Services (Preliminary) Examination 2022, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.