Question 680863: I am having trouble with this problem? Can someone please help me?
Dustin takes one hour to drive 40 miles from home to work every morning. He spends 30 minutes driving on the highway, 20 minutes driving on city roads, and 10 minutes driving on country roads. If he drives at the same speed on the country roads and the city roads, and travels 3 miles on the country roads, what is his average speed in miles per hour on the highway?
Answer by MathTherapy(10551)   (Show Source):
You can put this solution on YOUR website!
I am having trouble with this problem? Can someone please help me?
Dustin takes one hour to drive 40 miles from home to work every morning. He spends 30 minutes driving on the highway, 20 minutes driving on city roads, and 10 minutes driving on country roads. If he drives at the same speed on the country roads and the city roads, and travels 3 miles on the country roads, what is his average speed in miles per hour on the highway?
Since he drove 3 miles on the country roads and spent 10 minutes there, then his speed on the country roads = 3/(10/60), or 3/(1/6), or 18 mph. His speed on the city roads is also 18 mph
As his speed on the city roads is 18 mph, the distance traveled on city roads = 18 * 20/60, or 18 * 1/3, or 6 miles
Since he traveled 3 miles on country roads, and 6 miles on city roads, then he must’ve traveled 40 – (3 + 6), or 40 – 9, or 31 miles on the highway
Traveling for 31 miles on the highway, for 30 minutes (˝ hr), his speed = 31/(˝), or 31 * 2, or  mph
You can do the check!!
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