Question 152908
The rate of motorcycle is 40 mph greater than the rate of a bicycle.  The motorcycle travels 150 miles in the same amount of time as the bicycle travels 30 miles.  Find the rate of the motocycle.


m=rate of motorcycle
b=rate of bike
m=b+40


150/b+40=30/b-----------------------because miles over mph gives you the time, which is equal in this case.


Cross multiply
150b=30b+1200


Subtract 30b from both sides
120b=1200


Divide both sides by 120
b=10


m=b+40
m=10+40
m=50


Answer:
Bike=10mph
Motorcycle=50mph
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two people working together can do a job in 3 hrs.  How long will it take the slower person to do the same job if one of them is 3 times as fast as the other?


together=1/3 (of the job in an hour)
one person=x
other person=3x


x+3x=1/3


Combine like terms
4x=1/3


Divide both sides by 4
x=1/12


1/12 of the job in one hour, so the whole job in 12 hours.


Answer: The slower person can do the job alone in 12 hours.
* The faster person can do the job alone in 4 hours.