Download 5.1 Ratio and Proportion

5.1 Ratio and Proportion
Learning Objectives:
1. Write ratios as fractions.
2. Write rates as fractions and find unit rates.
3. Determine whether proportions are true.
4. Find an unknown number in a proportion.
5. Solve problems by writing proportions.
6. Key Vocabulary: ratio, rate, unit rate, proportion, cross product.
A. Ratios
Ratio—is the quotient of two quantities.
Three ways to write a ratio:
a
1. a to b
2.
b
3. a : b
Example 1. Write the ratio as a fraction in simplest form: 6.6 miles to 10 miles
B. Writing Rates as Fractions
Rates are used to compare different kinds of quantities.
Example 2. Write the rate as a fraction in simplest form:
6 tests for 30 students
C. Proportions
Proportion—is a statement that two ratios or rates are equal.
Using Cross Products Rule to Determine Whether Proportions Are True or False
Example 3. Determine whether the proportion
3 4
= is true or false.
6 8
D. Finding Unknown Numbers in Proportions
Example 4. Solve the proportion.
1
n
=
1 19
9
2
E. Applications
Example 5. Use proportion to solve the following application.
The ratio of students to faculty is 25 to 2. How many faculty members will be needed for a student
population of 625?