Page 114 - Math Course 3 (Book 2)

Properties of Proportions
Mo. 10

Lesson 1
Let’s Begin

KEY CONCEPTS:
Write a Ratio
1. Write ratios.
2. Use properties of proportions.
Example

SCHOOL
MO. 10 - L1a The total number of students who participate in
sports programs at Central High School is 520.
Writing Ratios The total number of students in the school is 1850.
Find the athlete-to-student ratio to the nearest
tenth.

Vocabulary A-Z

Let us learn some vocabulary

ratio
A ratio is a comparison of two quantities using
division. The ratio of a to b can be expressed as To find this ratio, divide the number of athletes by
a/b, where b is not zero. This ratio can also be the total number of students.
written as a:b.
number of athletes 520
= or about 0.3

3 total number of students 1850
0.3
8 1 : 1 0.3 can be written as .
1
1 : 2
2 : 3 Answer The athlete-to-student ratio is 0.3.

3 : 5
Extended Ratios in Triangles

proportion Example
An equation stating that two ratios are equal is
called a proportion.

TEST
25 1 EXAMPLE In a triangle, the ratio of the measures
of three sides is 5:12:13, and the perimeter is 90
100 = 4 centimeters. Find the measure of the shortest side
of the triangle.
2 6 A 15 cm B 18 cm C 36 cm D 39 cm
10 : 20 = 2 : 4 =
3 9 Read the Item
You are asked to apply the ratio to the three
sides of the triangle and the perimeter to find
the shortest side.

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