Question 870877: Grace's average driving speed is 10 mph faster than Tom's. In the same length of time, it takes Grace to drive 280 miles, Tom only drives 230. What is Grace's average speed?
Answer by JulietG(1812)   (Show Source):
You can put this solution on YOUR website! What is the difference in the distance between Grace and Tom? 280-230=50
What is the difference in the RATE of speed? 10 mph [given]
If she drives 50 miles further at a rate of 10mph faster, they drive for five hours (50/10)
If she drives 280 miles in 5 hours, her speed is 280/5, or 56 mph
If he drives 230 miles in 5 hours, his speed is 230/5, or 46 mph
The average is her speed + his speed, divided by 2. (56+46)/2, or 102/2, or 51 mph.
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