A train P going at the speed of 30 km/hr completely passes train Q of length 296 m, going in the same direction on parallel tracks, at 21 km/hr, in 6.5 minutes. How much time (in seconds) will P take to cross completely train R of length 196 m, going at 96 km/hr in the opposite direction?​

Correct option is C

Given:

Speed of train P = 30 km/h

Speed of train Q = 21 km/h (same direction)

Length of train Q = 296 m

Time to cross Q = 6.5 min = 390 seconds 

Length of train R = 196 m

Speed of train R = 96 km/h

We need to find the length of train P first.

Formula Used:

Relative speed (same direction) = Difference of speeds

Distance = Speed × Time

Solution: 

Length of P + Q's length = $$(30 - 21)\times\frac{5}{18} \times (6.5 \times 60)$$ 

P's length + 296 = 975 

P's length =  975 - 296 = 679 m 

Now, 

Length of train R = 196 m

Total distance to be covered = 679 + 196 = 875 m

Time to cross R (opposite direction) = $$\frac{875}{(30 + 96)\times \frac{5}{18}} = \frac{875}{35}$$​= 25 seconds