SOLUTION: I drove to my parents' house, 600 miles away. My mother worried that I drove too fast, so I promised her that when I drove home, I would slow down. I reduced my speed by 10 miles p

Question 763010: I drove to my parents' house, 600 miles away. My mother worried that I drove too fast, so I promised her that when I drove home, I would slow down. I reduced my speed by 10 miles per hour, but the trip took two hours longer. How fast did I drive each way.
Answer by josgarithmetic(39621) (Show Source): You can put this solution on YOUR website!
Let r = speed going to Mother.

WHICHWAY____________rate____________time______________distance
To Mother___________r_______________(___)_____________600
Back Home__________r-10_____________(___)_____________600

Fill in the time information, only as expressions.
WHICHWAY____________rate____________time______________distance
To Mother___________r_______________(600/r)_____________600
Back Home__________r-10_____________(600/(r-10))_____________600

Going back home took two hours longer.

Stated another way, the time going to mother plus two more hours was the amount of time spent driving back home. This is how that equation is formed.
Solve for r.
Begin by multiplying both sides of the equation by r(r+10) which will clear the denominators as you begin simplifying.

mph

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