Question

James can jog twice as fast as he can walk. He was able to jog the first 9 miles to his grandmother's house , but then he tired and walked the remaining 1.5 miles. If the total trip took 2 hours, then what was his average jogging speed.

Answer 1

James' jogging speed is 6 miles/hr

Step-by-step explanation:

Let x miles/hr be the speed that James walks at

Then, 2x miles/hr is the speed that James runs at

If James runs for 9 miles, ie

2

x

miles

=

1

hour

9

miles

=

a

hour

where a is a constant

a

=

9

2

x

hours

If James walks for 1.5 miles ie

x

miles

=

1

hour

1.5

miles

=

b

hours

where b is a constant

Since James travels for a total of 2 hours,

1.5

x

+

9

2

x

=

2

3

+

9

2

x

=

2

6

x

=

2

x

=

3

Hence, James walks for

3

miles

/hr and runs for

6

miles

/hr