Train Questions: Crossing a Pole/Tree

Question 04

A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively. What is the speed of the train?

Let length of the train be z meter

Given, time taken by the train to cross the telegraph post = 8 seconds

Since, Speed of the train =   Length of the train/Time taken to cross the telegraph

                                        =   z/8         ………………………………………………eq.(1)


 And, time taken by the train to cross the 264 m long bridge = 20 seconds

 Since, Speed of the train =     (Length of the train + Length of the platform)/ Time taken to cross the platform

                                          =     (z + 264)/20               …………………………………eq.(2)

From eq.(1) and eq.(2)

          z           =         z + 264

        20z         =     8 (z + 264)

        20z         =     8z + 2112

        20z – 8z =     2112

        12z         =     2112

       z           =      2112/12

       z           =      176 m

putting value of z = 176 in eq.(1)

Speed of the train = 176/8

                             =  22 m/sec.

                             =  22 * (18/5) km/hr.

                             = 79.2 km/hr.

Leave a Comment

Your email address will not be published. Required fields are marked *

You cannot copy content of this page