In how many hours were they 100 kilometers apart?

Question

Mr. Anders & Ms. Rich each drove home from a business meeting. Mr. Anders traveled east at 100 kilometers per hour & Ms. Rich traveled west at 80 kilometers per hour. 

Answer 1

First remember the distance formula:   d=rt

This means that distance is equal to rate of speed x time.

 

Mr Anders' distance from the staring point will be 100t  where t is time in hours

Ms Rich's distance from the staring point will be 80t where t is time in hours

 

Since they are going in opposite directions, you can find the total distance between them by adding there distances from the starting point.  We want to know when this distance is 100 so we can solve with the equation:

 

100t + 80t = 100

180t = 100   <--- Combine like terms

t = 5/9 or 0.5555... hours  <--- Divide by 180 on each side.

 

Therefore the answer is 5/9 of an hour or a bit more than 1/2 hour.