# Math Help - Problem solving with Quadratics x3

1. ## Problem solving with Quadratics x3

Jack and Mack both drive 40 km from home to work each day. One day Jack said to mack, "if you drive home at your usual speed, i will average 40 kmph faster than you and arrive home in 20 minutes less time." Find mack's speed.

2. Originally Posted by Tessarina
Jack and Mack both drive 40 km from home to work each day. One day Jack said to mack, "if you drive home at your usual speed, i will average 40 kmph faster than you and arrive home in 20 minutes less time." Find mack's speed.
Again, V= D/T and T= D/V.

Letting T be Mack's speed and V Mack's time, then T= 40/V. Driving 40 minues faster and 20 min= 1/3 hour less, T- 1/3= 40/(v+40). T= 1/2+ 40/(V+ 40)= 40/V. Solve for V.

3. Originally Posted by HallsofIvy
Again, V= D/T and T= D/V.

Letting T be Mack's speed and V Mack's time, then T= 40/V. Driving 40 minues faster and 20 min= 1/3 hour less, T- 1/3= 40/(v+40). T= 1/2+ 40/(V+ 40)= 40/V. Solve for V.