SOLUTION: Please help me! Starting at home, Jessica travelled uphill to the hardware store for 75 minutes at just 4 mph. She then travelled back home along the same path downhill at a sp

Question 887023: Please help me!
Starting at home, Jessica travelled uphill to the hardware store for 75 minutes at just 4 mph. She then travelled back home along the same path downhill at a speed of 12 mph.
What is her average speed for the entire trip from home to the hardware store and back?

Found 3 solutions by josgarithmetic, MathTherapy, Alan3354:
Answer by josgarithmetic(39615)   (Show Source): You can put this solution on YOUR website!
Same distance d both ways.
RT=D rate time distance.

_______________rate________time_________distance
UP_____________4_____________________d
DOWN__________12___________t______________d

Simplify the UP time hours and compute d:

_______________rate________time____________distance
UP_____________4_____________________d=4(5/4)=5
DOWN__________12___________t_________________d=5

The time going DOWN can now easily be computed as

Total distance is BOTH WAYS, up and down miles.
Total time in hours is hours.

Average Speed, , miles per hour.

Answer by MathTherapy(10551)   (Show Source): You can put this solution on YOUR website!
Please help me!
Starting at home, Jessica travelled uphill to the hardware store for 75 minutes at just 4 mph. She then travelled back home along the same path downhill at a speed of 12 mph.
What is her average speed for the entire trip from home to the hardware store and back?

On uphill trip, distance traveled: , or 5 miles
On downhill trip, time taken: hr
Total distance: 2(5), or 10 miles
Total time: , or , or , or hours
Average speed =
Average speed = __________, or mph
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
Jessica travelled uphill to the hardware store at just 4 mph. She then travelled back home along the same path downhill at a speed of 12 mph.
---------
The distance does not matter.
Avg speed for a round trip is similar to parallel resistors.
Avg = 2*4*12/(4+12) = 6 mi/hr

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