Section 7 1 Ratios and Proportions Objectives To

Section 7 -1: Ratios and Proportions

Objectives To write ratios and solve proportions.

Vocabulary Ratio Proportion Extended Proportion Cross-Product Property Scale Drawing Scale

Ratio A ratio is a comparison of two quantities. If you are comparing a to b, you may write as a proportion: Fraction form: _______ (b ≠ 0) Ratio form: a : b

Example A photo is 8 in. wide and 5 1/3 in high. It is enlarged to a poster that is 2 ft. wide and 1 1/3 ft. high. What is the ratio of the width of the picture to the width of the poster?

Proportion A proportion is a statement that two ratios are equal. You can write a proportion in the following forms:

Extended Proportion When three or more ratios are equal, you can write them as an extended proportion. Example:

Properties of Proportions:

Cross-Product Property The product of the extremes is equal to the product of the means. Also known as “Cross-Multiplying”

Solve the proportion:

Scale Drawing A scale drawing is a drawing in which all lengths are proportional to corresponding actual lengths.

Scale A scale is the ratio of any length in a scale drawing to the corresponding actual length. The lengths may be different units.

Geography Example Students at the University of Minnesota in Minneapolis built a model globe 42 ft. in diameter using a scale of 1: 1, 000. About how tall is Mount Everest on the model if it is actually about 29, 000 ft tall?