Download Math 6

KEY
LESSON 1: WHAT IS A RATIO?
A ratio is a pair of non-negative numbers, A:B, where both are not zero. It is a
relationship between two numbers.
A ratio can be written in three ways:
a to b
a:b
a
b
The numbers a and b in a ratio are called terms.
The order of the numbers is important to the meaning on the ratio. Switching the
numbers changes the relationship. The description of the ratio relationship tells us the
correct order for the numbers in the ratio.
LESSON 1: RATIOS
Example 1:
The coed soccer team has four times as many boys on it as it has girls. We say the ratio
of the number of boys to the number of girls on the team is 4:1. We read this as “four to
one.”
Total #
# of Boys
# of Girls
Of Players
4
1
5
If total was 10
8
2
If # of girls was 3
12
15
Suppose the ratio of number of boys to number of girls on the team is 3:2.
# of Boys
3
6
9
# of Girls
2
4
If # of girls was 6
Total #
Of Players
5
If total was 10
15
Example 2:
Make a tape diagram (or bar model) that shows that there are 3:2 as many boys to girls.
Boys
Girls
Example 3:
In the cafeteria, 100 milk cartons were put out for breakfast. At the end of breakfast,
27 remained. 100 – 27 = 73
a. What is the ratio of milk cartons taken to total milk cartons? 73:100 or 73 to 100
73
or
100
b. What is the ratio of milk cartons remaining to milk cartons taken? 27:73 or 27 to
27
73 or
73