Question

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?
a. 69.5 km/hrb. 70 km/hr c. 79 km/hr
d. 79.2 km/hr
​

Answer 1

Answer:

d) 79.2 kmph

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Step-by-step explanation:

Length of the Bridge = 264 m.

Time taken to pass the bridge = 20 sec.

Time taken to passe the post = 8 sec.

Length of the train = X m (Let.)

To pass the bridge train need to cover Train's length + Bridge legnth  (X +264).

Speed = Distance covered / time taken

Now,

X/8 = (264 + X)/20

20X = 264 *8 + 8X

20X - X = 264 *8

12X = 264 *8

X = (264 *8)/12

X = 176 m.

Speed of the train = 176/8 = 22 m/sec = (22*18)/5 = 79.2 Kmph.