A roadside magician/tricks -player in Jalpaiguri (West Bengal) demonstrates his skill of climbing up a pole fitted on the ground. He performs this feat before the audience who encourage him sufficiently. It was observed that in the first minute he takes 15 seconds to climb one metre. After that in the next minute he shows the public that he climbs down. For that he takes 20 seconds to climb down. He repeats this process of climbing up for the first minute and climbing down in the next minute. After how many minutes will he reach the top of a pole of 42 metre height and decides to stay there and show public?

a) 77 min b) 84 min c) 79 min d) cannot be ascertained.

• a) 77 min
  
  In the first minute he climbs up 4 metres of the pole. (he climbs 1 metre in 15 seconds. Therefore he climbs 4 metres in 60 seconds i.e 1 min)
  In the next minute he goes down 3 metres of the pole. So at the end of 2 minutes he has gone up by 1 metre. (he climbs down 1 metre in 20 seconds. Therefore he climbs down 3 metres in 60 seconds i.e 1 min)
  Assuming, this process is repeated he will take 76 minutes to reach 38 metre height of the pole.
  And in the next minute he will be able to reach 42 metre top and stays there.
  Thus he takes 77 minutes to do this.
• 10 years agoHelpfull: Yes(0) No(0)