SOLUTION: Jon recently drove to visit his parents who live 60 miles away. On his way there his average speed was 9 miles per hour faster than on his way home (he ran into some bad weather).

Question 1149792: Jon recently drove to visit his parents who live 60 miles away. On his way there his average speed was 9 miles per hour faster than on his way home (he ran into some bad weather). If Jon spent a total of 3 hours driving, find the two rates.
Answer by ikleyn(52797) (Show Source): You can put this solution on YOUR website!
.

If x is the slower rate (in miles per hour), then the faster rate is (x+9) mph.


The "time" equation is


     +  = 3  hours.


Simplify


     +  = 1


then multiply both sides by x*(x+9)


    20*(x+9) + 20x = x*(x+9)

    20x + 180 + 20x = x^2 + 9x

    x^2 - 31x - 180 = 0

     =  =  = .


Only positive root makes sense  x =  = 36.


Answer.  The slower rate is 36 mph;  the faster rate is  36+9 = 45 mph.

Solved.

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Using "time" equation is the STANDARD method of solving such problems.
From this lesson, learn on how to write, how to use and how to solve a "time" equation.

To see many other similar solved problems, look into the lessons
    - Had a car move faster it would arrive sooner
    - How far do you live from school?
    - Earthquake waves
    - Time equation: HOW TO use, HOW TO write and HOW TO solve it
in this site.

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