A straight railway track has trains plying on it at a constant speed of 100 km / h. Two trains which are one after another pass a certain point on the track at an interval of 6 min. On a straight road parallel to the track, a car is moving in the same direction as the trains, at a speed of 60 km / h. At what time interval (in minute) the consecutive trains pass by the car?

Question

A straight railway track has trains plying on it at a constant speed of 100 km / h. Two trains which are one after another pass a certain point on the track at an interval of 6 min. On a straight road parallel to the track, a car is moving in the same direction as the trains, at a speed of 60 km / h. At what time interval (in minute) the consecutive trains pass by the car? (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

Separation between trains =100 km / h × 6 min Now speed of trains relative to car =100-60=40 km / h If t is the interval of time passing through car, then 40 × t=100 × 6 ⇒ t=(100/40) × 6 min =15 min

Separation between trains =100km/h×6min Now speed of trains relative to car =100−60=40km/h If t is the interval of time passing through car, then 40×t=100×6 ⇒t=40100​×6min=15min

Separation between trains $= 100 km / h \times 6 min$
Now speed of trains relative to car $= 100 - 60 = 40 km / h$
If $t$ is the interval of time passing through car, then
$40 \times t = 100 \times 6$
$\Rightarrow t = \frac{100}{40} \times 6 min = 15 min$