Pre-Algebra Solving Proportions

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Pre-AlgebraSolving Proportions
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What Are You Learning?

• I CAN solve proportions.

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Why Do You Need To Know This?

• Proportions can be used to compare different
  types of items.
• Proportions are useful because they allow objects
  to be compared equally.
• They can be used many ways in the real world.

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Vocabulary

• Proportionan equation that shows that two ratios
  are equivalent.
• Cross Productthe product of the numerator of one
  ratio and the denominator of the other ratio.

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Notes

• 1 3
• 2 6
• 1 x 6 is a cross product.
• 2 x 3 is a cross product.
• The cross products of a proportion are equal.
• Two ratios form a proportion if their cross
  products are equal.

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Determine whether each pair of ratios form a
proportion.

1. 25/40 and 5/8
2. 13/15 and 4/5
3. 49/21 and 28/12

1. ¾ and 9/12
2. 8/12 and 14/21
3. 4/5 and 5/6

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Notes

• Solving the proportionProcess of using cross
  products to find a missing term in a proportion.
  
• Solving a proportion is similar to solving an
  equation.

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Example

• x 4
• 9 6
• x 6 9 4 (Cross multiply)
• 6x 36 (Solve for the variable)
• 6x 36 (Divide to undo multiplication
• 6 6
• x 6

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Solve each proportion. When necessary, round to
the nearest tenth.

• 15/30 n/34
• h/36 21/27
• 26/15 130/m

1. 36/j 7/20
2. r/23 17/34
3. 77/93 x/24