Train B which is ‘d’ meter long can cross a pole in 35 seconds. Train A can cross a platform of (d+10) meter long in (t+45) seconds. The ratio between the lengths of train A and B is 9:7 respectively. Train B can cross train A in (3t-70) seconds.If the difference between the speeds of both trains is 4 m/s, then find out the value of ‘t’.

Solution

Let’s assume the speeds of train A and B are ‘Sa‘ and ‘Sb‘ respectively.

The ratio between the lengths of train A and B is 9:7 respectively.

Let’s assume the lengths of train A and B are 9y and 7y respectively.

Train B which is ‘d’ meter long can cross a pole in 35 seconds.

So d = 7y

7y = 35xSb

y = 5xSb   Eq.(i)

Train A can cross a platform of (d+10) meter long in (t+45) seconds.

(7y+10) = (t+45)xSa   Eq.(ii)

Train B can cross train A in (3t-70) seconds. If the difference between the speeds of both trains is 4 m/s.

(9y+7y)/(3t-70) = 4

16y = 4(3t-70)

4y =(3t-70)   Eq.(iii)

In Eq.(i), Eq.(ii) and Eq.(iii), there are a total of four variables. We cannot determine the value of ‘t’ from the given information.