SOLUTION: David and Keith are route drivers for a fast -photo company. David route is 80 miles, and Keith�s is 100 miles. Keith averages 10 mph more than David and finishes his route 10 minu

Question 323778: David and Keith are route drivers for a fast -photo company. David route is 80 miles, and Keith�s is 100 miles. Keith averages 10 mph more than David and finishes his route 10 minutes before David. What is David�s speed.
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Equation for David:

Equation for Keith:

By substitution:

Multiply both sides by

Use the quadratic formula

For David:

David's speed is 30 mi/hr
check:
For Keith

OK
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