Question

On the number line, a bug P is moving in the positive direction from the point 0, and a bug N is moving in the negative direction from the point 0. The speeds of both bugs are constant. Both leave 0 at the same time, and four seconds later P has reached 12 and N has reached –8. 30 seconds after leaving point 0, how far apart are P and N?

Answer 1

They are 150 units apart.

Since P travels in a positive direction 8 units in 4 seconds, this means that P's speed is 2 units/sec.

Since N travels in a negative direction 12 units in 4 seconds, this means that N's speed is -3 units/sec.

After 30 seconds, P will have traveled 2(30) = 60 units.
After 30 seconds, N will have traveled -3(30) = -90 units.

60--90 = 150.