Here are the key points about ratios: - A ratio expresses the relationship between two quantities. It can be written as A:B, A/B, or "A to B". - "Per" and "for every" indicate a ratio. For example, "2 miles per hour" means the ratio of miles to hours is 2:1. - Part to part (P/P) ratios compare two parts of a whole, like the ratio of girls to boys. Part to whole (P/W) ratios compare a part to the whole, like the ratio of girls to total students. - P/W ratios can be thought of as fractions because they relate a part to the whole. P

1. RATIOS
7. RP. 1 AND 2a, 2b
Objective: Explain Ratio, Part to Part, Part to Whole, and
solve for a ratio problem.

2. START UP:
There are 21 people in the classroom. There are 2
girls for every 3 people in the classroom. How
many girls are there? How many boys?
There are 20 people in the classroom. There are 2
girls for every 3 boy in the classroom. How many
girls are there? How many boys?

3. NOTES:
A ratio is a relationship between two quantities. A
ratio can be written as A:B, A/B or by the phrase
“A to B”.
Per (mph, $/item, grade/class, )
This can be part to whole or Part to Part. (P/W or
P/P)
Looks like a Fraction (but not always!) only in Part
to whole

4. PART TO WHOLE RELATIONSHIP
There are men and woman in a meeting. If the ratio of
woman to people in a room is 3 to 5 and there are 40
people in the room, how many women are in the room?
Part to whole: woman to people
3:5 is 3 woman: 5 people OR
3/5 is 3 woman/5 people (this CAN be thought of as
a fraction because it is a part to whole relationship)

5. PART TO WHOLE RELATIONSHIP
Part to whole: woman to people
3:5 is 3 woman: 5 people OR
3/5 is 3 woman/5 people (this CAN be thought of as
a fraction because it is a part to whole relationship)
WOMEN PEOPLE MEN
3 5
6 10
9 15
Finish this chart

6. PART TO WHOLE RELATIONSHIP
WOMEN PEOPLE MEN
3 5 2
6 10 4
9 15 6
12 20
15 25
18 30
21 35
24 40

7. PART TO PART RELATIONSHIP
There are men and woman in a meeting. If the ratio of
woman to MEN in a room is 3 to 5 and there are 40
people in the room, how many women are in the room?
Part to part: men to woman
3:5 is 3 woman to 5 men OR
3/5 is 3 woman to 5 men (this CANNOT be thought
of as a fraction because it is a part to part relationship)

8. PART TO PART RELATIONSHIP
Part to part: men to woman
3:5 is 3 woman to 5 men OR
3/5 is 3 woman to 5 men (this CANNOT be thought
of as a fraction because it is a part to part relationship)
WOMEN PEOPLE MEN
3 5
6 10
9 15
Finish this chart

9. PART TO PART RELATIONSHIP
WOMEN PEOPLE MEN
3 8 5
6 10
9 15
12 20
15 25
If the ratio of woman to MEN in a room is 3 to 5 and
there are 40 people in the room, how many women are in
the room?

10. Explain your understanding
What a ratio and what does “per” and
“for every” mean?
What is the difference between P/P and
P/W
There are 7 girls for every 8 boys in the
grade. If there are 135 kids in the grade,
how many boys and girls are there?