With 51 gallons of fuel in its tank, the airplane has a weight of 2390.7 pounds. what is the weight of the plane with 81 gallons of fuel in its tank? the slope is 5.7

2561.7 pounds

Explanation:

If we assume the total weight of an airplane (in pounds units) as a linear function of the amount of fuel in its tank (in gallons) and we make a Weight vs amount of fuel graph, which resulting slope is 5.7, we can use the slope equation of the line:

 (1)

Where:

is the slope of the line

is the airplane weight with  51 gallons of fuel in its tank (assuming we chose the Y axis for the airplane weight in the graph)

is the fuel in airplane's tank for a total weigth of 2390.7 pounds (assuming we chose the X axis for the a,ount of fuel in the tank in the graph)

This means we already have one point of the graph, which coordinate is:

Rewritting (1):

 (2)

As Y is a function of X:

 (3)

Substituting the known values:

 (4)

 (5)

 (6)

Now, evaluating this function when X=81 (talking about the 81 gallons of fuel in the tank):

 (7)

 (8)   This means the weight of the plane when it has 81 gallons of fuel in its tank is 2561.7 pounds.

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