Question 665333: bob's work is 40 miles away from his home. His average mph to work is 20. his average mph from work to his home is 40 mph what is the average mph for the whole trip
At first i thought it was 30, but then i thought it was a trick question because it takes 2 hours for bob to get to work and only takes 1 hour for bob to get home from work
Found 2 solutions by ankor@dixie-net.com, MathTherapy:
Answer by ankor@dixie-net.com(22740)   (Show Source):
Answer by MathTherapy(10555)  (Show Source):
You can put this solution on YOUR website!
The most important thing to note here is that:
Average speed equals total distance, divided by total time
Since each trip is 40 miles, then total distance for entire trip = 2 * 40, or 80 miles
Since his speed for 1st part of trip (home to work, which is 40 miles) is 20 mph, then it took him  , or 2 hours to get to work
Since his speed for 2nd part of trip (work to home, which is 40 miles) is 40 mph, then it took him  , or 1 hour to get back home
Applying the formula, we now get average speed as:  , or  , or  mph
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