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WBCS Preliminary Examination 2020 — General Studies · Question 177 of 200

Q177
ReasoningSeating Arrangement, Ranking & Puzzles
A caterpillar crawls up a pole 75 inches high, starting from the ground. Each day it crawls up 5 inches and each night it slides down 4 inches. When will it first reach the top of the pole?
  1. a.The 70th day
  2. b.The 71st day
  3. c.The 72nd day
  4. d.The 75th day

Answer: (B) The 71st day

The caterpillar makes a net gain of 1 inch per full day-night cycle, reaching 70 inches after 70 days; on the 71st day, its daytime climb of 5 inches takes it from 70 to 75 inches, reaching the top before it can slide back.