Question

John can jog twice as fast as he can walk. He was able to jog the first 5 miles to his grandmother's house, but then he tired and walked the remaining 2 miles. If the total trip took 0.9 hours, then what was his average jogging speed?

Answer 1

Explanation:

Suppose, John walks with a speed x

Then, John can jog at a speed 2x

`total \: time \: = (total \: distance)/(average \: speed)`

TOTAL TIME

`</strong><strong>0.9</strong><strong> = </strong><strong> (5)/(2x) + (2)/(x)`

Further solving :

x = 5 mph

Average jogging speed (2x) = 10 mph

Answer 2

10mph

Explanation:

We know that John's total trip is 0.9 hours, so let's try to figure out how much of that time is spent jogging, and how much of it is spent walking.

We can do that by naming the time he takes to jog a mile y.

An equation would be:

5y+2(2y)=0.9

5y+4y=0.9

y=0.1

It takes him 0.1 hours, or 6 minutes to jog a mile.

Since he jogged 5 miles, his jogging time is 0.5 hours, or 30 minutes.

Now,

Let's name the speed he jogs x (miles per hour)

This allows us to set up another equation.

Note that:

Speed=distance/time

His jogging speed is x.

x=5/0.5

x=10

His average jogging speed is 10 miles an hour.