Download DO NOW (not later):

Unit 3/ Module 5: RATIO
Today we will learn about…..
Ra-T-o??
-OR-
Ra-sh-o??
Lets do a comparison within
our class….

Compare the number of boys to girls
in THIS class.

The number of boys =

The number of girls =

If we compare boys to girls we get
9 boys to 11 girls.
9 boys to 11 girls.
This comparison (ratio) can be written three different ways…
Part to part--- 9 to 11
9: 11
or Part to whole---- 9 out of 20
9/11
Basically a RATIO is a comparison of two (or more) quantities
to establish a relationship between them.
When/where do we see ratios used in
our everyday life?
Consumer data…
9:10 dentist recommend
When writing a ratio, ORDER does matter.

Cooking/Recipes
A recipe for cookies uses 3 cups of flour
and 2 cups of milk---- 3:2




What would the cookies taste like
if you
if you followed the ratio of
2:3 instead??????
Driving


Mr. Benny drove 135 miles in 3 hrs
135:3
Use of ratio in school….

class-size 22:1

love school lunch 7:10

Johnny raises his hand 9:10
What is a ratio?
A relationship between two
numbers of the same kind
When writing a ratio, ORDER does matter
HERE WE ARE COMPARING FRUIT…
6 ORANGES TO 7 APPLES……
7 APPLES TO 6 ORANGES……
6:7
7:6
YOU MUST WRITE THE RATIO EXACTLY AS IT WILL BE
ASKED.
It’s Friday night and your friends are having a
party……
The ratio of girls to guys is 2 to 12.
Would you want to attend the
party?
How many basketballs to footballs are
there?
For every 4 basketballs
there are 6 footballs.
 The ratio is 4 to 6.

What are some other ways we
can write the ratio of basketball
to footballs?
Every ratio can be written in 3 ways:



4 to 6
First quantity to Second quantity
4:6
First quantity : Second quantity
4
6
First quantity divided by the second
quantity (as a fraction).
Careful!!
Order matters in a ratio.
4 to 6
Is NOT the same as
6 to 4
Equivalent Ratios can be formed by
multiplying the ratio by any number.

For example, the ratio 2 : 3 can also be
written as



4 : 6 (multiply original ratio by by 2)
6 : 9 (multiply original ratio by by 3)
8 : 12 (multiply original ratio by by 4)
The ratio 2 : 3 can be expressed as
2x to 3x (multiply the original ratio
by any SAME number x)
A bag contains 18 yellow, blue, and red marbles. The
ratio of yellow to blue to red marbles is 4 : 2 : 3.
1)
2)
3)
Write the ratio of yellow to blue marbles in
simplest form.
What is the ratio of yellow to red marbles?
How many yellow marbles are there?
You can compare ratios part to part as show
above OR part to whole.
Ex. How many red marbles to the whole (or total)
amount of marbles?
 Lets do some group practice.
Quick review of group expectation…
*respect your group member… take turns &
listen more than you speak
* No chiefs… everyone’s an Indian! No bossy
take-over behaviors.
* Speak at a volume that your group (not entire
class) can hear you.