A recipe uses 2 cups of sugar for 5 cups of flour. How many cups of sugar are needed for 15 cups of flour?

A recipe uses 2 cups of sugar for 5 cups of flour. How many cups of sugar are needed for 15 cups of flour?

• A. 4
• B. 5
• C. 8
• D. 6

Answer: (D)

Keep a constant ratio: two cups of sugar for every five cups of flour. When flour goes from five to fifteen cups, that’s three times as much flour. The sugar must rise by the same factor, so multiply by three: two times three equals six cups of sugar. In other words, tripling the flour requires tripling the sugar to keep the same balance. The final amount is six cups of sugar.

Keep a constant ratio: two cups of sugar for every five cups of flour. When flour goes from five to fifteen cups, that’s three times as much flour. The sugar must rise by the same factor, so multiply by three: two times three equals six cups of sugar. In other words, tripling the flour requires tripling the sugar to keep the same balance. The final amount is six cups of sugar.