Question

Two trains P and Q are equal in length. Train P takes 1 second less to cross a platform of length 450 m than train Q.  The speed of P is 1m/s more than that of Q. Find the speed(in m/s) of P.
1. 60
2. 63
3. 50
4. 57

Answer 1

Correct Answer - Option 3 : 50

Given:

Two trains P and Q are equal in length. Train P takes 1 second less to cross a platform of length 450 m than train Q.  The speed of P is 1m/s more than that of Q. 

Formula:

If the lengths of two trains are a and b,

Time taken to cross each other when travelling in same direction = (a + b)/(va - vb)

Time taken to cross each other when travelling in opposite direction = (a + b)/(va + vb)

where va and vb are the speeds of trains A and B respectively.

Calculation:

Let the length of each train be l.

Let speeds of P and Q be v + 1 and v respectively.

⇒ (l + 450)/(v + 1) = (l + 450)/v – 1

⇒ v = 49

Speed of P = v + 1 = 49 + 1 = 50 m/s.