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?

6 mile/hour

Explanation:

Let the speed of walking of James = x mile/hour

speed of jogging = 2x mile/hour

9/2x + 1.5/x = 2

= > (9 + 3) / 2x = 2

= > 12 = 4x

= > x = 3

Average speed of walking = 3 mile/hour

Average speed of jogging = 2 * 3 = 6 mile/hour