Question

Two trains A and B are running in same direction. Faster train crosses the slower train in 20 seconds. If length of A is 200 m and speed of A and B is 40 m/s and 10 m/s respectively, then find the length of B.
1. 200 m 
2. 300 m 
3. 400 m 
4. 500 m
5.

Answer 1

Correct Answer - Option 3 : 400 m 

Given:

Both trains cross each other in 20 seconds while running in the same direction

Length of A = 200 m 

Speed of A and B is 40 m/s and 10 m/s respectively

Concept used:

If two objects are running in the same direction, then their relative speed becomes subtraction of their speed

Formula used:

Distance = Speed × Time

Calculation:

Let the length of B be x  

Here, A and B are running in same direction

So, According to the concept, we have

Relative speed  = (40 - 10) m/s = 30 m/s

Now, according to the formula, we have

(200 + x) m = (30 × 20) m

⇒ x = (600 - 200) m = 400 m 

∴ The length of B is 400 m.

When two trains cross each other, the total distance becomes the sum of their length.