Understanding Direct Proportionality

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Math › Understanding Direct Proportionality

Questions 1 - 3

1

Sarah notices her map has a scale of $\frac{1}{4}; in=1; mile$ . She measures between Beaver Falls and Chipmonk Cove. How far apart are the cities?

Explanation

$\frac{1}{4}; in=1; mile$ is the same as

So to find out the distance between the cities

$12.5; in \cdot \frac{4; miles}{1;in }=50; miles$

2

Sunshine paint is made by mixing three parts yellow paint and one part red paint. How many gallons of yellow paint should be mixed with two quarts of red paint?

(1 gallon = 4 quarts)

Explanation

First set up the proportion:

$\frac{3; parts ; yellow}{1 ; part; red}=\frac{x ; quarts ; yellow}{2 ; quarts ; red}$

x =

Then convert this to gallons:

$6 ; quarts; \cdot \frac{1 ; gallon}{4; quarts}= 1.50; gallons$

3

If is directly proportional to , and when , find a formula for .

$\frac{y}{4}=x$

$y=\frac{x}{4}$

Explanation

since and

Solving for , you get that

Replacing in the original equation, you get the answer of

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