SOLUTION: A group of students held a car wash to raise money. They charged $9 for each car and $12 for each van or SUV. Two teams worked continuously, one washing cars and the other washin

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A group of students held a car wash to raise money. They charged $9 for each car and $12 for each van or SUV. Two teams worked continuously, one washing cars and the other washin      Log On


   



Question 841180: A group of students held a car wash to raise money. They
charged $9 for each car and $12 for each van or SUV. Two teams worked
continuously, one washing cars and the other washing vans and SUVs.
The team washing cars required 25% less time per vehicle than the other
team. Each team washed vehicles for 4 hours. The two teams together
raised a total of $720. How long, on average, did each team take to wash
a vehicle?

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = the number of cars the
car washing team washed in 4 hrs
Let +b+ = the number of vans and
SUVs the other team washed in 4 hrs
If I increase the ( time/vehicle ) for the car
washers by 25%, that equals the
( time/vehicle ) for the van/SUV washers
---------------------------------
(1) +4%2Fa+%2B+.25%2A%28+4%2Fa+%29+=+4%2Fb+
(2) +9a+%2B+12b+=+720+
--------------------------
Multiply both sides of (1) by +a%2Ab+
(1) +4b+%2B+b+=+4a+
(1) +5b+=+4a+
(1) +b+=+%284%2F5%29%2Aa+
-------------------
Substitute (1) into (2)
(2) +9a+%2B+12b+=+720+
(2) +9a+%2B+12%2A%284%2F5%29%2Aa+=+720+
(2) +9a+%2B+%2848%2F5%29%2Aa+=+720+
Multiply both sides by +5+
(2) +45a+%2B+48a+=+3600+
(2) +93a+=+3600+
(2) +a+=+38.71+
and
(1) +b+=+%284%2F5%29%2Aa+
(1) +b+=+%284%2F5%29%2A38.71+
(1) +b+=+31+
-------------------
+a%2F4+=+39%2F4+
+a%2F4+=+9.75+
and
+b%2F4+=+31%2F4+
+b%2F4+=+7.75+
-----------------
The car-washers average 9.75 vehicles/hr
The van/SUV washers average 7.75 vehicles/hr
check:
(2) +9%2A39+%2B+12%2A31+=+720+
(2) +351+%2B+372++=+720+
(2) +723+=+720+
close enough
(1) +b+=+%284%2F5%29%2Aa+
(1) +31+=+.8%2A39+
(1) +31+=+31.2+
OK
You might want a 2nd opinion on this
the numbers seem a little strange