Question

Mary can jog twice as fast as she can walk. She was able to jog the first 13.5 miles to

her grandmother's house, but then she tired and walked the remaining 1.5 miles. If the
total trip took 1.5 hours, then what was her average jogging speed?

Answer 1

Answer: Let's call Mary's walking speed "w". Then, her jogging speed is 2w.

The total distance of the trip was 13.5 + 1.5 = 15 miles.

The total time she spent jogging was 1.5 hours, so the time she spent walking was 1.5 - 1.5 = 0 hours.

Her average speed for the whole trip was 15 miles / 1.5 hours = 10 miles per hour.

So, we can set up the equation:

(13.5 miles / 2w) + (1.5 miles / w) = 1.5 hours

We can substitute 2w for jogging speed and w for walking speed, and simplify:

(13.5 miles / 2w) + (1.5 miles / w) = 1.5 hours

13.5 / 2w + 1.5 / w = 1.5

27 / 2w = 1.5

2w = 27 / 1.5

2w = 18

Finally, we can find Mary's jogging speed by dividing the expression for 2w by 2:

w = 18 / 2

w = 9

So, Mary's jogging speed was 9 miles per hour.

Explanation: