How much time elapses before the two cars collide? Two cars, A and B, are 400 meters apart. Car A travels due east at 30 meters per second on a collision course with car B which travels due west at 20 meters per second.
A. 2s
B. 8.0s
C. 20s
D. 40s

The correct answer to this question is B. If two cars are 400 meters apart and a collision occurs while one is traveling east at 30 meters per second and the other is traveling west at 20 meters per second, you would need to solve for x to find out how much time elapsed before the two cars collided.

To do this, you would multiply one speed of 30 by the time of x to the other speed of 20 to the time of x to equal the distance of 400 meters. When you add the 30x and the 20x, you get 50x. You would then need to divide 400 by 50 to get x which equals 8 seconds.