Question

Q. A man in a train notices that he can count 31 poles in one minute. If they are known to be 50metres apart, then at what speed is the train travelling?​

Answer 1

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21 posts would mean 20 blocks of 50 metres each. Total distance covered = 20 x 50 metres = 1000 metres in 1 min or 1 Km in 1 min = 60 Km in 60 mins = 60 Km/hr = 60 x (5/18) m/s = 16.67 m/s.

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there are 21 poles and each pole is 50 m apart.

distance between 1st an 21st pole = (21–1) *50 = 1000 m = 1 km

time = 1 min = 1/60 km

speed = distance / time

= 1/ (1/60) km/h

= 60 km/h

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Given:

No. of poles= 21

Distance between them= 50m

=>Total distance= 20*50m= 1000m=1km

Time taken is= 1min = 1/60 hr

Speed = distance/time;

=> speed=1/(1/60) =1*60 =60kmph

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The train is travelling at the speed of 63kmph.

21 poles at a distance of 50 metres.

21 x 50 = 1050 metres.

21 poles in a minute = 1050 metres in a minute.

1050 metres x 60 minutes = 63000 metres in an hour.

So 63 kilometres in an hour.

hope it helps you