Section 2'5 Formulas

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Section 2.5Formulas

• Definition of Formula
• Formula Rule
• Facts from Geometry
• Basic Percent problems

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Definition Formula

• In mathematics, a formula is an equation that
  contains more than one variable.
• P 2L 2W

L
W
W
L
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Example 1

• The perimeter of a rectangular livestock pen is
  40 feet. If the width is 6 feet find the length.
• P 40
• W 6
• P 2L 2 W
• (40) 2L 2(6)
• 40 2 L 12
• 28 2L
• 14 L

W 6
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Example 2 Page 117

• 3x 2y 6
• x 4
• Find y

• 3(4) 2y 6
• 12 2y 6
• -12 -12
• 2y -6
• y -3

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Consider the formula for the area of a triangle
Solve for h

• Multiply by 2
• Divide both sides by b

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Rule page 118

• To solve a formula for one of its variables we
  must isolate that variable on either side of the
  equal sign.
• All other variables and constants will appear on
  the other side.

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Example 4Solve for v
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Solve for h
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Facts from Geometry Complementary Angles
Complementary AnglesCombine to form a 90o angle.
Right angle 90o
1
2
Angle 1 Angle 2 90o
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Facts from Geometry Supplementary Angles
Supplementary AnglesCombine to form a 180o angle.
Straight angle 180o
1
2
Angle 1 Angle 2 180o
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Facts from Geometry

• Complimentary angles have a sum of 90.
• x y 90
• If we solve this formula for y we obtain a
  formula equivalent to our original formula.
• y 90 x
• This formula gives us y which is the complement
  of x.

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Complements and Supplements

• What is the complement of 25?
• y 90 x
• y 90 25
• y 65
• What is the supplement of 25?
• y 180 x
• y 180 25
• y 155

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Percentages Example 6

• What number is 25 of 60?
• W .25(60)
• W 15

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Percentages Example 7

• What percent of 24 is 6?
• 6 (24)
• 6 p(24)

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Percentages Example 8

• 45 is 75 of what number?
• 45 75(b)
• 45 .75(b)

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Homework

• Problem set 2.5
• Page 124
• 1- 93 Odd