A muffin recipe calls for 2 1/2 cups of flour for every 2/3 cups of sugar. How many cups of flour should be used when 4 cups of sugar are used?

4 / (2/3)

4 * (3/2) + 12/2 = 6

6 * 2.5 = 15 cups of flour

Correction:

4 * (3/2) = 12/2 = 6

To find out how many cups of flour should be used when 4 cups of sugar are used, we need to set up a proportion using the given ratio of flour to sugar in the muffin recipe.

The ratio states that for every 2/3 cups of sugar, 2 1/2 cups of flour are needed.

Let's set up the proportion:

(2 1/2 cups of flour) / (2/3 cups of sugar) = (x cups of flour) / (4 cups of sugar)

To solve for x (the number of cups of flour to be used when 4 cups of sugar are used), we can cross-multiply and solve for x.

Cross-multiplying gives us:

(2 1/2 cups of flour) * (4 cups of sugar) = (2/3 cups of sugar) * (x cups of flour)

10 cups of flour = (2/3) * (x cups of flour)

Now, we need to solve for x. To do so, we can divide both sides of the equation by 2/3:

10 cups of flour = (x cups of flour) * (3/2)

Simplifying:

10 cups of flour = (3/2) * (x cups of flour)

Next, we can divide both sides of the equation by (3/2) to isolate x:

x cups of flour = (10 cups of flour) / (3/2)

Now, let's simplify this division:

x cups of flour = 10 cups * (2/3)

x cups of flour = 20/3 cups

x cups of flour = 6 2/3 cups

Therefore, when 4 cups of sugar are used, you should use approximately 6 2/3 cups of flour in the muffin recipe.

I agree with 15.