Question

james can jog twice as fast as he can walk. he was asked to jog the first 9 miles to his grandmothers house but then he tired and walked the remaining 1.5 miles. if the total trip took 2 hours what was his average jogging speed?

Answer 1

let
x--------> time it takes to jog (hours)
y--------> time it takes to walk (hours)

we know that
x+y=2-----> x=2-y-----> equation 1
x=2y-----> equation 2
equate equation 1 and equation 2

2-y=2y------> 2y+y=2-----> 3y=2-----> y=2/3 hours
x=2*(2/3)----> x=4/3 hours

find the average jogging speed
speed=distance/time
distance=9-1.5-----> 7.5 miles
time=2/3 hour
speed=7.5/(2/3)----> 7.5*(3/2)---> 11.25 miles/hour

the answer is
11.25 miles/hour