Question 1028613
A girl starts to walk to her school, which is 20 miles away, at 6:50 and at a rate of 3 miles per hour.
 After a while, her dad picks her up and drives her through the remainder of the way at 30 miles per hour.
 If they arrived at school at 9:00, how far did she walk? 
:
Find the total time it took her to get to school: 9:00 - 6:50 = 2 hrs 10 min
Change this to hrs; 2 {{{1/6}}}hrs which is {{{13/6}}} hr
:
let w = distance walked
the total dist is 20 mi, therefore
(20-w) = distance driven
:
Write a time equation, time = dist/speed
Walk time + drive time = {{{13/6}}} hrs
{{{w/3}}} + {{{(20-w)/30}}} = {{{13/6}}}
get rid of the fractions, multiply equations by 30, then cancel
10w + (20-w) = 5(13)
10w - w = 65 - 20
9w = 45
w = 45/9
w = 5 miles walked
;
:
Check this by finding the actual time walking (5mi) and riding (15mi)
5/3 = 1.67 hrs
15/30 = .5 hrs
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total time 2.17 hrs which is 2 hrs 10 min