Solving Proportions

Front

What is a proportion?

Back

A proportion is an equation that states that two ratios are equal. For example, if a/b = c/d, then a, b, c, and d are in proportion.

Front

How do you solve a proportion?

Back

To solve a proportion, you can use cross-multiplication. If a/b = c/d, then a*d = b*c.

Front

What is cross-multiplication?

Back

Cross-multiplication is a method used to solve proportions by multiplying the numerator of one ratio by the denominator of the other ratio.

Front

If 3/4 = x/12, what is x?

Back

x = 9. (Cross-multiply: 3*12 = 4*x, so 36 = 4x, and x = 36/4 = 9.)

Front

What is the first step in solving a proportion?

Back

The first step is to set the two ratios equal to each other.

Front

What does it mean if two ratios are equivalent?

Back

If two ratios are equivalent, it means they represent the same relationship between quantities.

Front

If 5/10 = x/20, how do you find x?

Back

x = 10. (Cross-multiply: 5*20 = 10*x, so 100 = 10x, and x = 100/10 = 10.)

Front

What is the relationship between the means and extremes in a proportion?

Back

In a proportion a/b = c/d, the means are b and c, and the extremes are a and d. The product of the means equals the product of the extremes.

Front

What is an example of a real-life situation that can be solved using proportions?

Back

If a recipe calls for 2 cups of flour for 4 servings, how much flour is needed for 10 servings? (Use proportions to find the answer.)

Front

What is the formula for finding a missing value in a proportion?

Back

If a/b = c/x, then x = (b*c)/a.