Question 102404: Mary and Jocelyn are sisters. They left the school at 3:00 P.M. and bicycled home along the same bike path. Mary bicycled at a speed of 12 mi/h. Jocelyn bicycled at 9 mi/h. Mary got home 15 min. before Jocelyn. How long did it take Mary to get home?
Define a variable(s), set up and solve.
Answer by josmiceli(19441)   (Show Source):
You can put this solution on YOUR website! In these kind of problems, bikes, trains, boats, etc. it
really helps if the first question you ask is "what is the
same for both?" In this case it's the distance from school to home,
and also, they both start at 3 PM.
Notice everything else is different.
 holds true for both
For Mary,
 in minutes
 in mi/hr
For Jocelyn,
 in mi/hr
Now write equations
 because they're going the same distance, so call
them both 
 (Note I converted 15 minutes to .25 hrs)
Now for Jocelyn,
Now set the equations equal to eachother
 in hours
Mary got home a quarter hour before Jocelyn, so
 in hours
Or, Mary's time was 45 minutes
You should chck these answers by putting them back in the
original equations
 in miles
and
in miles
So, you get the same answer for school - home distance
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