Question

Q14
A train crosses a pole in 12 sec and a bridge of
length 170 m in 36 sec. Then the speed of the
train is:
30.75 km/hr
10.8 km/h
25.5 km/hr
32.45 km/hr​

Answer 1

Step-by-step explanation:

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Answer 2

If train cross its length in 12 seconds and 170 m bridge in (36 - 12 = 24) seconds.

Speed of train = [170/24] × [18/5] = 25.5 km/hr

Detailed method:

Let the length of the train be x m.

As we know,

Speed = Distance/time

Speed = x/12 ---(1)

Speed = (x + 170)/36 ---(2)

Frome equation (1) and equation (2)

x/12 = (x + 170)/36

⇒ 3x = x + 170

⇒ 2x = 170

⇒ x = 170/2

⇒ x = 85 m

From equation (1)

Speed = 85/12 × (18/5) km/hr

∴ Speed = 25.5 km/hr