RATIOS and PROPORTIONS REVIEW

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RATIOS and PROPORTIONS REVIEW

• By Teachers who care!

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RATIOS PROPORTIONS

• A ratio is a comparison of two numbers by
  division.
• To write ratios, use the word to, a colon, or a
  fraction bar.
• EXAMPLE 1 John read 3 books in 4 days. Write
  the ratio of books to days.

Words 3 to 4
Colon 34
Fraction 3/4
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RATIOS PROPORTIONS

• A proportion is a statement that two ratios are
  equal.

EXAMPLE2 Is a proportion?
Find the cross products.
30 30 TRUE
If TRUE, the statement is a proportion.
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RATIOS PROPORTIONS
EXAMPLE3 Is a proportion?
Find the cross products.
20 21 FALSE
If FALSE, the statement is NOT a proportion.
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RATIOS PROPORTIONS
EXAMPLE4 Solve the proportion
Find the cross products.
Divide both sides by 10.

• 10

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RATIOS PROPORTIONS
There are 5 boys and 6 girls in Grant School.
1. What is the ratio of girls to boys using a
fraction?
2. What is the ratio of girls to children in
Grant School (use a colon)?
611
3. What is the ratio of boys to children in
Grant School (use words)?
5 to 11
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RATIOS PROPORTIONS
Are the following proportions?
FALSE Not a proportion
FALSE Not a proportion
TRUE this is a proportion
TRUE this is a proportion
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RATIOS PROPORTIONS
Find the missing numbers to make the following
proportions.
10 10
9 9
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SCALE DRAWINGS

• A scale drawing is a drawing of an object with
  dimensions proportional to those of the actual
  object. To find lengths from scale drawings, set
  up and solve proportions.

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SCALE DRAWINGS USING PROPORTIONS

• EXAMPLE1 ¼ in 5 ft is a scale for a rock
  bands concert stage.

A. The scale length of the drum stand is 1 in.
What is the actual length of the drum stand?
Cross multiply.
Divide by .25
.25 .25
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SCALE DRAWINGS USING PROPORTIONS

• EXAMPLE2 ¼ in 5 ft is a scale for a rock
  bands concert stage.

B. The actual length of the stage is 60 ft.
What is the scale length of the stage?
Cross multiply.
Divide by 5
5 5
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SCALE DRAWINGS USING PROPORTIONS

• Given a scale of ½ in 4 ft, find the actual
  length for each scale length given.

.5 .5
.5 .5