Proportional Reasoning Math Example 4

Follow the full solution, then compare it with the other examples linked below.

Example 4

easy
A recipe that serves 4 people uses 10 cups of flour. How many cups are needed to serve 10 people?

Solution

  1. 1
    Set up the proportion: 10 cups4 people=x cups10 people\frac{10 \text{ cups}}{4 \text{ people}} = \frac{x \text{ cups}}{10 \text{ people}}.
  2. 2
    Cross-multiply: 4x=10×10=1004x = 10 \times 10 = 100.
  3. 3
    Solve: x=100÷4=25x = 100 \div 4 = 25 cups.

Answer

25 cups25 \text{ cups}
When quantities scale together at a constant rate, set up equal ratios and cross-multiply to find the unknown.

About Proportional Reasoning

The ability to recognize and work with multiplicative relationships between quantities. If one quantity doubles, a proportional quantity also doubles — the ratio stays constant.

Learn more about Proportional Reasoning →

More Proportional Reasoning Examples

Example 1 easy

If 3 notebooks cost $7.50, how much do 7 notebooks cost?

Example 2 medium

A recipe calls for 2 cups of flour for every 3 cups of sugar. If you use 9 cups of sugar, how many c

Example 3 medium

A map uses a scale of 1 cm : 25 km. Two cities are 7.5 cm apart on the map. What is the actual dista

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