SOLUTION: How do I solve this? "Philip drove 12 miles in town in the same time he drove 19 miles on the highway. His highway speed was 21 miles per hour faster than his speed in town. Wh

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Question 958678: How do I solve this?
"Philip drove 12 miles in town in the same time he drove 19 miles on the highway. His highway speed was 21 miles per hour faster than his speed in town. What was his average speed on the highway?"
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39799)   (Show Source): You can put this solution on YOUR website!
RT=D uniform rates rule for travel.

___________________speed___________time__________distance
IN TOWN_____________r________________t____________12
HIGHWAY_____________r+21_____________t____________19



Variable assignments implied in the table.


You want to solve for r and evaluate r+21.
Answer by MathTherapy(10810)   (Show Source): You can put this solution on YOUR website!

How do I solve this?
"Philip drove 12 miles in town in the same time he drove 19 miles on the highway. His highway speed was 21 miles per hour faster than his speed in town. What was his average speed on the highway?"
Let speed on highway, be S

Then speed in town = S - 21

We then get: 

19(S - 21) = 12S -------- Cross-multiplying

19S - 399 = 12S

19S - 12S = 399

7S = 399

S, or speed on highway = , or  mph 

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