<PRE><B>Question 384449</B>
Susan decided to run the store which is 8km from her house.
 She ran at a rate of 7km per hour for part of the way and than walk at a
 rate of 3km per hour the rest of the way.
 if the total trip took 2 hrs how many km did she run
:
Let x = distance ran
then
(8-x) = distance walked
:
Write a time equation; time = dist/speed
:
Time ran + time walked = 2 hrs
{{{x/7}}} + {{{((8-x))/3}}} = 2 hrs
Multiply by 21, results
3x + 7(8-x) = 21(2)
3x + 56 - 7x = 42
3x - 7x = 42 - 56
-4x = -14
4x = 14
x = {{{14/4}}}
x = 3.5 km ran
then
8 - 3.5 = 4.5 km walked
;
:
Check, find times of each
3.5/7  = .5 hrs
4.5/3 = 1.5 hrs
-----------------
total = 2.0 hrs


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