Question 375952
A family has two cars. The first car has a fuel efficiency of 40 miles per gallon of gas and the second has a fuel efficiency of 30 miles per gallon of gas. During one particular week, the two cars went a combined total of 1650 miles, for a total gas consumption of 45 gallons. How many gallons were consumed by each of the two cars that week?
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one car 40  miles /gallon
other car 30 miles/gallon
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Total miles = 165 
gas used = 45 gallons
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let first car drive x miles
second car drive y miles
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x/40 + y/30 = 45
(30x+40y)/30*40 = 45
30x+40y = 45*40*30
30x+40y=54,000............................1
x+y = 1650...............................2
multiply (2) by -30
-30x-30y= 1650*-30
-30x-30y=-49,500

add to (1)
10y=4500
/10
y=450 miles
average = 30
consumption = 450/30
= 15 gallons
x= 1650-450=1200 miles
first car 1200/40 = 30 gallons

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m.ananth@hotmail.ca