Question 564822
Sarah takes 40 minutes to walk to her office and only 12 min if she rides her bike.
 Her speed when walking is 7 miles per hour less than her speed when riding her bike. (assume she takes the same path to her office).
 What is the distance to her office.
:
Let s = his walking speed
then
(s+7) = his biking speed
:
Write a distance equation; dist = speed * time
We need the time in hrs
:
{{{40/60}}}s = {{{12/60}}}(s+7)
Reduce the fractions
{{{2/3}}}s = {{{1/5}}}(s+7)
Multiply by 15 to clear the denominators
5(2s) = 3(s+7)
10s = 3s + 21
10s - 3s = 21
7s = 21
s = 21/7
s = 3 mph is his walking speed
:
Find the distance
{{{2/3}}}(3) = 2 miles
Check the distance
{{{1/5}}}(3+7) = 2 miles also