A recipe calls for 2 1/2 cups of flour for every 1 1/4 cups of sugar. If you want to make a larger batch using 5 cups of flour, how many cups of sugar will you need?
Correct: A
Let f be the amount of flour and s be the amount of sugar. We have the proportion f/s = 2.5/1.25. We are given f = 5. Thus, 5/s = 2.5/1.25. Cross-multiplying, we get 2.5s = 5 * 1.25 = 6.25. Dividing by 2.5 gives s = 6.25 / 2.5 = 2.5. So the answer is 2 1/2.