Question

A train 300 m long crosses a bridge 500m long in 40 seconds. Find the speed of the train in km/h.​

Answer 1

GIVEN :

Length of train = 300m

Length of bridge = 500m

Time taken to cross the bridge = 40sec

We know that,

Speed = Distance/Time taken

Total Distance = 300 + 500 = 800m

= 800/40

= 20m/s

Multiply 18/5 to convert into km/h

=> 20 × 18/5

=> 4 × 18

=> 72km/h

Therefore, the speed of train is 72km/h.

Answer 2

Answer :-

Speed in Km/h = 72 Km/h

Solution :-

Length of the train = 300 m

Length of the bridge which is crossed by train = 500 m

Time taken to cover the bridge by train = 40 seconds

Distance covered by train to cross the bridge = Length of the train + Length of the bridge which is crossed by train = 300 + 500 = 800 m

$\boxed{ \sf Speed = \dfrac{Distance}{Time} }$

Here

• Distance(d) = 800 m

• Time(t) = 40

$\sf s = \dfrac{800}{40}$

$\sf s = \dfrac{80}{4}$

$\sf s = \dfrac{80 \div 4}{4 \div 4}$

$\sf s =20$

So, speed in m/s = 20 m/s

Convert m/s into Km/h

To convert multiply it by 18/5

s = 20 * 18/5

s = 4 * 18

s = 72

So, speed in Km/h = 72 Km/h