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, thus x = 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

How can proportions be used in real life?

Back

Proportions can be used in real life for tasks such as cooking (adjusting recipes), map reading (scale), and financial calculations (interest rates).

Front

What is the relationship between ratios and proportions?

Back

Ratios compare two quantities, while proportions state that two ratios are equal.

Front

If 5/8 = 15/x, what is x?

Back

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

Front

What is a unit rate?

Back

A unit rate is a ratio that compares a quantity to one unit of another quantity, such as miles per hour.

Front

How do you find a missing value in a proportion?

Back

You can find a missing value by setting up a proportion and using cross-multiplication to solve for the unknown.