Rate time distance question

[Abdulla]

While on a straight road, car X and car Y are traveling at different constant rates. If car X is now 1 mile ahead of car Y, how many minutes from now will car X be 2 miles ahead of car Y ?

(1) Car X is traveling at 50 miles per hour and car Y is traveling at 40 miles per hour.

(2) 3 minutes ago car X was 1/2 mile ahead of car Y.

OA is D

[palvarez]

You can solve this problem, if you know relative speed.

(1) relative speed = 40-30 = 10

(2). relative distance = 1 - (1/2) = 1/2 mile
relative speed = (1/2)(1/(3/60)) = 10


D is the answer.

10 miles per 60 minutes = 1 mile per every 6 minutes.

2 miles ahead, and currently 1 mile ahead. The relative distance = 1 miles. 6 more mins required.

[Abdulla]

Thanks palvarez. It is a good tip.