Question 340067
sue drove at a rate of 45 mph from her home to her sister's house.
 she spent 1 1/2 hours having lunch with her sister.
 she then drove back home at a rate of 55 mph. the entire trip including lunch took 4 hours.
 how far does sue live from her sister?
:
We are only interested in her travel time: 4 - 1.5 = 2.5 hrs
:
Let d = distance to sisters house (and back)
:
Write a time equation: time = dist/speed
{{{d/45}}} + {{{d/55}}} = 2.5
:
Multiply by 2475 (that's 45*55) to get rid of the denominators, results
55d + 45d = 2475(2.5)
:
100d = 6187.5
d = {{{6187.5/100}}}
d = 61.875 ~ 62 miles
:
:
Check solution by finding the time each way
62/45 = 1.38 hrs
62/55 = 1.13 hrs
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total: 2.51 hrs, close enough