SOLUTION: An engineer traveled 170 mi by car and then an additional 645 mi by plane. The rate of the plane was three times the rate of the car. The total trip took 7 h. Find the rate of the

Let x = the rate of the car, in miles per hour.

Then the rate of the plane is 3x miler per hour.



The time equation is


     +  = 7 hours,

or

     +  = 7,


     = 7,


    x =  = 55.


ANSWER.  The car rate was 55 miles per hour.