help me with this problem

Question

here is my question: Sam left for school at 8:00, walking at a speed of 2 mph. Soon after, his father discovered that Sam left behind his project that was due that same day. Sam's father left home 20 minutes after Sam, and his average speed (he was driving) was 12 mph. At what time will Sam's father give the project to Sam? help!

Answer 1

It is easier to sketch these, but think of it this way.

 

Sam leaves at 8.0 and is traveling 2 mph -- so the distance he travels in X time is (X - 8.00)2mph

Dad leaves at 8.33 (20 minutes after 8) and travels at 12 mph,so his distance in X time is (X - 8.33)12 mph

You want to know when the times are the same...

So set the two equal to each other and solve for X.

 

After you do the work, remember that an answer like 8.4 means 4/10 of an hour after 8, or 24 minutes...