SAT Math · Two-variable data: models and scatterplots · easy

The equation C = 3.5g + 40 models the total cost C, in dollars, of a rental car after driving g gallons' worth of fuel, including a fixed…

The equation C=3.5g+40C = 3.5g + 40 models the total cost CC, in dollars, of a rental car after driving gg gallons' worth of fuel, including a fixed rental fee. What does the value 3.5 represent in this model?

Answer and explanation

Answer: C: The cost, in dollars, increases by $3.50 for each additional gallon of fuel used.

In C=3.5g+40C = 3.5g + 40, the cost CC depends linearly on gg, the gallons of fuel. The coefficient of gg is the slope, which is the rate of change: each additional gallon adds $3.50 to the total cost. That is choice C. The constant 40 is the starting cost when g=0g = 0, the fixed fee. Choice A claims 3.5 is the total cost, but total cost changes with gg. Choice B mentions days, but the variable is gallons. Choice D says 3.5 is the initial fee, but the initial fee is 40, the intercept. Slope means rate; intercept means starting amount.

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