Worked examples
Two examples
Example 1
A recipe uses 3 cups of flour for 24 cookies. How many cups of flour for 40 cookies?
- Set up the proportion, cups over cookies on both sides: 324 = x40.
- Cross-multiply: x × 24 = 3 × 40 = 120. x = 120 ÷ 24.
Answer: 5 cups
Example 2
On a map, 1 inch stands for 25 miles. Two towns are 3.5 inches apart on the map. How far apart are they?
- Each inch is 25 miles, so multiply: 3.5 × 25.
Answer: 87.5 miles
Where this is taught: Ratio, Proportion, and Percent, “Setting up a proportion”
The drill
Ten problems
This drill also has challenge problems. They use the same skill, set up the way the GED test sometimes sets up a problem, so that it looks new at first.
How many:
Type the number only; the unit is already there. Then press Check my answers at the bottom.Write each answer on the line. The answer key, with the reasoning, is on the last page.