One car travels 200 mi. A second car, traveling 10mi/h faster than the first car, makes the same trip in 1hr less time. Find the speed of the slower car.

Answer 1

Let x = speed of slower car and T = the travel time of the slower car

xT = 200 => T=200/x

The equation for the other care then is

(x+10)(T-1)=200

SUbstitute

(x+10)[(200/x)-1]=200

Multiply by x

(x+10)(200-x)=200x

Expand and collect

x² + 10 x - 2000 = 0

The quadratic formula gives an extraneous root and x = 40.

You should be able to finish from here.