Question

Two commuter rail cars, one from Shah Alam and the other from Kuala Lumpur approach each other on parallel tracks. Each has a speed of 100km/h with respect to the earth. If they are initially 10km apart, how long will it be before they pass each other?

Answer 1

They meet after the time t from the departure

During this time, one goes through the distance

S1 = V1 * t

and the second goes through the distance

S2 = V2 * t

The sum of the two distances gives us total distance

S1 + S2 = S

Replace S1 and S2 in this last equation

V1 * + V2 * t = S

t (V1 + V2) = S where we take out the time they meet

t = S / (V1 + V2)

V1 = V2

t = 10 / 2V1 = 10/200 = 0.05 hours