Try either finding how many cups of flour are needed for 1 muffin, or set up a fraction like $\frac{2}{8} = \frac{x}{20}$ and solve for $x$.

Make sure you are keeping the same order in both ratios: cups over muffins in both fractions, not cups over muffins in one and muffins over cups in the other.

In Desmos, type the expression (2/8)*20 to represent "2 cups for 8 muffins, scaled up to 20 muffins." Use the value that Desmos outputs as the number of cups of flour needed.

The recipe says 2 cups of flour makes 8 muffins. This is a ratio of flour to muffins: $\frac{2\text{ cups}}{8\text{ muffins}}$.

You can think about this as either:

• cups of flour per muffin, or
• muffins per cup of flour.

Either way, the relationship stays the same when you scale up.

Option A: Unit rate
Find cups of flour per muffin:

This means each muffin needs $\frac{1}{4}$ cup of flour.

Option B: Proportion
Let $x$ be the cups of flour needed for 20 muffins. Set up:

Then solve this proportion for $x$.

Using the unit rate from Option A:

• Each muffin needs $\frac{1}{4}$ cup.
• For 20 muffins:

Using the proportion from Option B:

So, you need 5 cups of flour to make 20 muffins at the same rate.