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Ratios. Ratio is a way of comparing two or more quantities Examples: Number of oranges to apples Number of girls in a class compared to boys. Ratio?. There are 3 ways to express ratios :. As a fraction - ¾ Using a colon - 3:4 Using the word “to” - 3 to 4. - PowerPoint PPT Presentation
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Ratios
Ratio?
Ratio is a way of comparing two or more quantities
Examples:
◦Number of oranges to apples
◦Number of girls in a class compared to boys
There are 3 ways to express ratios:
As a fraction - ¾Using a colon - 3:4Using the word “to” - 3 to 4
What is the ratio of cats to mice?
Number of Cats: 3
Number of Mice: 6
Express the ratio as a fraction:
Express the ratio in words:
Express the ratio with a colon:
3 to 6
3:6
63
Team Wins Losses
S.D. Padres 16 11
L.A. Dodgers 18 13
Chicago Cubs 17 14
2001 Spring Training
List the wins to losses by the Cubs : 17 to 14
Wins to games played by the Cubs: 17 to 31
List the losses to wins by the Padres: 11/16
Losses to games played by the Padres : 11/27
Team Wins Losses
S.D. Padres 16 11
L.A. Dodgers 18 13
Chicago Cubs 17 14
2001 Spring Training
List the Dodgers wins to total games: 18 : 31
List the Dodgers losses to wins: 13 : 18
Your face uses about 13 muscles to smile and about 43 muscles to frown. Write the ratio of muscles used for frowning to muscles used for smiling in three different ways.
43:13
43/13
43 to 13
Comparing Ratios Seth and Nathan compared their CD
collections. To determine who has a greater ratio of rock CDs to pop CDs, write the ratios.
Rock Pop Hip-hop
Seth 9 23 16
Nathan 42 70 25
Seth:
= .375
Nathan: = 0.6
Write ratios as fractions.
Write fractions as decimals to compare.
Nathan has a greater ratio of rock to pop CDs.
Pop
Rock
23
9
Pop
Rock
70
42
How do you change a fraction into a decimal?
Divide the denominator into the numerator
OR on your calculator hit 9 divided by 24 = .375
24
9
RED & BLUE Smarties
6 BLUE 3 RED
“The Ratio of BLUE to RED Smarties is 6 to 3
Blue : Red
6 : 3
Which symplifies to 2 : 1
“The Ratio of BLUE to RED Smarties is 6
Ratio Example Problems
…. Or… We can compare Red to Blue Smarties!
RED & BLUE Smarties
6 BLUE 3 RED
“The Ratio of RED to BLUE Smarties is 3 to 6”
Red : Blue
3 : 6
1 : 2
“The Ratio of RED to BLUE Smarties is 1:2”
“For every RED Smartie, there are 2 BLUES”
Simplifying Ratios
In the Smarties example, we changed 6:3 to 2:1
This is called Simplifying a ratio
We did it by dividing each number by 3
3 was the largest common factor
Try to simplify these
8:218:34:85:255:2
4:16:11:21:55:2 !!
Sharing an amount in a given ratio“Bart and Maggie share a bag of 16 life savers with the ratio of 3:1”
This means “for every 3 life savers Bart gets, Maggie gets 1”4
Lifesavers for Maggie
12Lifesavers for Bart
What is a ratio?
Example: There are 300 computers and 1200 students in our school. What is the ratio of computers to students?
Express the ratio in words:
Express the ratio as a fraction:
A ratio is a comparison
of two quantities.
Express the ratio with a colon:300 computers : 1200 students
How many students are there for one computer?
300 computers to 1200 students
𝟑𝟎𝟎𝒄𝒐𝒎𝒑𝒖𝒕𝒆𝒓𝒔𝟏𝟐𝟎𝟎𝒔𝒕𝒖𝒅𝒆𝒏𝒕𝒔
Equivalent ratios make
the same comparison.
What is an Equivalent Ratio?
1.There are 300 computers for 1200 students
Express the ratio as a fraction:
1200300
2.There is 1 computer for every 4 students
OR
Bring the fraction to lowest terms:
1200300
41
=
Practice With Equivalent Ratios
Find an equivalent ratio by dividing:
9030
Divide by 3031
= # 1
# 2 1215
45
= Divide by 3
# 3300125
125
= Divide by 25
30903030
÷÷
=
312315
÷÷
=
2530025125
÷÷
=
Practice With Equivalent Ratios
Find an equivalent ratio by multiplying:
410
Multiply by 554510
x x
= # 4
# 5
# 6
2050
=
37
12 x 312 x 7
=3684
= Multiply by 12
2011
6 x 206 x 11
=12066
= Multiply by 6
Practice:Ratios worksheet
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