# distance problem

• Feb 24th 2010, 01:08 AM
sri340
distance problem
John leaves home traveling to the next city at 50 mph. His sister Joann leaves home 30 minutes later, traveling the same route as John, but Joann travels 65 mph. How long will it take Joann to catch up with John?
• Feb 24th 2010, 01:11 AM
Emergency
just a tip. remember they are travelling per hour so in 30 min John would have already travelled 25miles. But his sister travels 32.5miles in 30 min. Think it through.
• Feb 24th 2010, 03:59 PM
satx
Quote:

Originally Posted by sri340
John leaves home traveling to the next city at 50 mph. His sister Joann leaves home 30 minutes later, traveling the same route as John, but Joann travels 65 mph. How long will it take Joann to catch up with John?

From the time Joann leaves, John's distance is f(t)=50t +25 , with f(t) being the distance in miles and t being the number of hours. Joann's distance is f(t)=65t. You want to find the t value for which 50t + 25 =65t.
• Feb 25th 2010, 01:35 AM
HallsofIvy
As Emergency said, when Joann leaves home she is 25 miles behind John. She is travelling 65- 50= 15 mph faster than John. How long will it take her to make up 25 miles at a relative speed of 15 mph?