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Suppose that the weight (in pounds) of an airplane is a linear function
of the amount of fuel (in gallons) in its tank.
When carrying 10 gallons of fuel, the airplane weighs 2055 pounds.
When carrying 42 gallons of fuel, it weighs 2231 pounds.
How much does the airplane weigh if it is carrying 46 gallons of fuel?
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It is a standard entertainment problem to solve it MENTALLY without using equations.
Airplane + 10 gallons of fuel weights 2055 pounds. (1)
Airplane + 42 gallons of fuel weights 2231 pounds. (2)
----------------------------------------------------------Subtract (2) from (1). You will get
32 gallons of fuel weight 2231 - 2055 = 176 pounds. ====>
====> 1 gallon of fuel weights = 5.5 pounds.
(Airplane + 46 gallons of fuel)'s weight = (Airplane + 42 gallons of fuel weight) + weight of 4 gallons of fuel =
= 2231 + 4*5.5 = 2253 pounds.
Answer. Airplane with 46 gallons of fuel weights 2253 pounds.
Solved.