Use Direct and Inverse Variation: exemplo 8.91

Problema e solução em inglês, como no livro original.

The fuel consumption (mpg) of a car varies inversely with its weight. A car that weighs 3100 pounds gets 26 mpg on the highway.

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Sua vez

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A car’s value varies inversely with its age. Elena bought a two-year-old car for $20,000.

ⓐ Write the equation of variation. ⓑ What will be the value of Elena’s car when it is 5 years old?

Como foi?

Sua vez

O Try It do livro logo depois deste exemplo: mesma ideia, outros números. Só a resposta é dada.

A car’s value varies inversely with its age. Elena bought a two-year-old car for $20,000.

ⓐ Write the equation of variation. ⓑ What will be the value of Elena’s car when it is 5 years old?

	The fuel consumption varies inversely with the weight.
First we will name the variables.	Let $f =$ fuel consumption. $w =$ weight
Write the formula for inverse variation.
We will use $f$ in place of $y$ and $w$ in place of $x$ .
Substitute the given values for the variables.

Solve for the constant of variation.

Write the equation that relates $f$ and $w$ .
Substitute in the constant of variation.

	The fuel consumption varies inversely with the weight.
First we will name the variables.	Let $f =$ fuel consumption. $w =$ weight
Write the formula for inverse variation.
We will use $f$ in place of $y$ and $w$ in place of $x$ .
Substitute the given values for the variables.

Solve for the constant of variation.

Write the equation that relates $f$ and $w$ .
Substitute in the constant of variation.