Question

A train which is travelling at a constant speed crosses a lamp post in 9 seconds and it takes 13.5 seconds to cross a platform 99 m long.Find the length of the train

a.99m b.198m c.135m d.12m
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Answer 1

Answer:

Let the length of the train be x meter.

Train crossed the pole is 2 sec. So distance covered in 2 sec. is x meter.

Hence, the speed of train = distance / time = x / 2 ——- (1)

In second case,

Total distance covered by train is = ( x + 250) meter

Time take = 7 second

So, speed of train = (x + 250 ) / 7 ——(2)

From (1) and (2)

x/2 = (x+250)/7

7x = 2x + 500

5x = 500

x = 100

Hence the length of train is 100m

Answer 2

let length of train=x meters

speed of the train =×/2 m/s

now

Step-by-step explanation:

speed in second case= (x+99)÷13.5

now

x/2=(x+99)÷13.5

13.5x=(x+99)9

13.5x=9x+891

4.5×=891

×=198m

short trick

if we observe options there is no chance for the 99 ,and 135 because they are int questions 12 m is very least value to compare with 99. so definitely answer will be 198 m