A cyclist drove one kilometre, with the wind in his back, in three minutes and drove the same way back, against the wind in four minutes. If we assume that the cyclist always puts constant force on the pedals, how much time would it take him to drive one kilometre without wind ?



A cyclist drove one kilometre, with the wind in his back, in three minutes and drove the same way back, against the wind in four minutes. If we assume that the cyclist always puts constant force on the pedals, how much time would it take him to drive one kilometre without wind ?

A. 7/3 min

B. 24/7 min

C. 17/7 min

D. 43/12 min

Answer : B. 24/7 min


Explanation :

  • Let the speed of the cyclist be 'x' km/h and wind be 'y' km/h.
    1 / (x + y) = 3/60
    ⇒ x + y = 20 --------> (i)
    And, 1 / (x − y) = 4/60
    ⇒ x − y = 15 --------> (ii)
  • On solving both the equations we get:
    x = 35/2
    y = 5/2
  • Now, time taken by cyclist without wind:
    = 2/35 × 60
    = 24/7 min

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