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 scale factor in a proportion?

Back

The scale factor is the ratio of any two corresponding lengths in two similar geometric figures.

Front

If 5/8 = 15/x, how do you find x?

Back

x = 24. (Cross-multiply: 5*x = 8*15, so 5x = 120, and x = 120/5 = 24.)

Front

What does it mean for two ratios to be equivalent?

Back

Two ratios are equivalent if they represent the same relationship between quantities, meaning they can be expressed as a proportion.

Front

How can you check if two ratios are in proportion?

Back

You can check if two ratios are in proportion by cross-multiplying and seeing if the products are equal.

Front

What is a unit rate?

Back

A unit rate is a comparison of two different quantities when they are combined together, expressed as a quantity per one unit of another quantity.

Front

If a recipe calls for 2 cups of flour for every 3 cups of sugar, what is the ratio of flour to sugar?

Back

The ratio of flour to sugar is 2:3.