Question

3. To make purple frosting, you start with white frosting.
Then you add 2 drops of red food coloring and 3 drops of
blue food coloring. If 4 red drops come out with the first
squeeze, how many blue drops should you add?

Answer 1

Answer:  6 drops of blue

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Explanation:

We basically mix red and blue to get purple. The ratio needed is 2 parts red, and 3 parts blue. We can shorten this by writing 2:3

Note how we can double both parts of the ratio to get 4:6, showing that 4 drops of red correspond to 6 drops of blue, which is the answer we want.

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Another approach:

x = some positive real number

(2 parts red)/(3 parts blue) = (4 parts red)/(x parts blue)

2/3 = 4/x

2x = 3*4 .... cross multiply

2x = 12

x = 12/2 .... divide both sides by 2

x = 6

So 6 drops of blue go with 4 drops of red.