*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**.