Question

Mr. Granger, a cyclist, rode from his home to his office at an average speed of 18 miles per. On his return home from his office, using the same route, he averaged 12 miles per hour. If the total trip took 5 hours, what was the distance from his home to his office?

Answer 1

The distance is 36 miles.

Explanation:

distance in either direction = d

total time = 5

time going = t

time returning = 5 - t

speed = distance/time

going:

speed = distance/time

18 = d/t

d = 18t Eq. 1

returning:

speed = distance/time

12 = d/(5 - t)

60 - 12t = d

d = 60 - 12t Eq. 2

Eq. 1 and Eq. 2 form a system of equations.

d = 18t

d = 60 - 12t

Since d = d, then 18t must equal 60 - 12t

18t = 60 - 12t

30t = 60

t = 2

d = 18t = 18(2) = 36

The distance is 36 miles.