8-1 RATIOS AND PROPORTIONSM11.C.1 2.8.11.D

Objectives:

1) To write ratios and solve proportions

VOCABULARY Ratio – a comparison of two quantities

Written as1. a to b 2. a : b

Reading Math: You can read a : b as “the ratio a to b”

EXAMPLES: REAL WORLD CONNECTIONS

A scale model of a car is 4 inches long. The actual car is 15 feet long. What is the ratio of the length of the model to the length of the car?

VOCABULARY A proportion is a statement that two ratios are

equal. You can write a proportion in these forms:

and a : b = c : dRead as “a is to b as c is to d”

When three or more ratios are equal, you can write an extended proportion.

Example:

PROPERTIES OF PROPORTIONS

is equivalent to…..

1) ad = bc2) 3) 4)

CROSS-PRODUCT PROPERTY

Multiplying the numbers on the diagonal result in: ad = bc

EXAMPLES: PROPERTIES OF PROPORTIONS If complete each statement:

A. 6x = _____B. ____C. _____D. _____

SOLVING PROPORTIONS Solve each proportion”

SCALE DRAWING A scale compares each length in a drawing to

the actual length.

Example: Two cities are 3.5 inches apart on a map with the scale 1 in = 50 miles. Find the actual distance.