The monthly cost of driving a car depends on the number of miles driven. Lynn found that in May it cost her $420 to drive 500 mi and in June it cost her $444 to drive 620 mi. (a) Express the monthly cost C as a function of the distance driven d, assuming that a linear relationship gives a suitable model. C(d)

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MrRoyal MrRoyal · Answer 1 · 2021-06-14T03:14:39+02:00

Answer:

[tex]C(d) = \frac{1}{5}d + 320[/tex]

Step-by-step explanation:

Given

[tex]d \to miles[/tex]

[tex]C \to cost[/tex]

So:

[tex](d_1,C_1) = (500,420)[/tex] --- May

[tex](d_2,C_2) = (620,444)[/tex] --- June

Required

Express as a function

Start by calculating the slope (m)

[tex]m = \frac{\triangle C}{\triangle d}[/tex]

[tex]m = \frac{444-420}{620-500}[/tex]

[tex]m = \frac{24}{120}[/tex]

Simplify

[tex]m = \frac{1}{5}[/tex]

The equation is:

[tex]C(d) = m(d - d_1) +C_1[/tex]

[tex]C(d) = \frac{1}{5}(d - 500) +420[/tex]

[tex]C(d) = \frac{1}{5}d - 100 +420[/tex]

Take LCM

[tex]C(d) = \frac{1}{5}d + 320[/tex]