Question

Two trains of length 220 m and 380 m long are running at the speed of 80 km/hr and 62 km/hr. In same direction. In how much time they will cross each other?​

Answer 1

Answer:

The trains will cross each other in $2$ $hours$ $22$ $minutes$ $and$ $30$ $seconds$.

Step-by-step explanation:

The lengths of the trains are 220 m and 380 m.

In order to match the units of speed, let's express these lengths in km

Therefore, the lengths are $\frac{220}{1000} km = 0.22 km$ and $\frac{380}{1000} km = 0.38 km$

At the start of journey, the front of both the trains are at same mark.

Therefore, the back of the faster train was 0.38km behind the front of the slower train.

The moment the faster train completely crosses the slower train, the back of the faster train crosses the front of the slower train.  .  .  .  .  .  .  .  (i)

Let's assume that, in t hours, the trains will cross each other.

In t hours the front of slower train will move 0.22t km

And in same t hours the back of the faster train will move 0.38t km

According to the requirement expressed by (i):

$0.38t = 0.38 + 0.22t$

$=>0.38t - 0.22t = 0.38$

$=>0.16t = 0.38$

$=>16t = 38$  [multiplying both sides by 100]

$=>t = \frac{38}{16} = \frac{19}{8}$

∴ The trains will cross each other in $\frac{19}{8} = 2\frac{3}{8}$ hours $= 2 hours \frac{3}{8} * 60 minutes$

$= 2 hours \frac{45}{2} minutes$ $= 2 hours 22.5 minutes$ $= 2 hours 22 minutes 30 seconds$