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Retail Math Formulas

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					Chapter 2 Section 4: Formulas
   In this section, we will…
     Use formulas to
     solve word problems
     Solve a formula
     for a given variable




2.4 Formulas
 We will use the following formulas from business:        simple interest
                                                          formula
   interest = principal  rate  time OR      i  prt         Don’t forget to
                                                           change your percent
                                                            to a decimal before
      profit = revenue - cost    OR       p  r c         using it in a formula!


  retail price = cost + markup      OR      r cm

 We will use the following formulas from science:

        distance = rate  time    OR      d  rt

       5( F  32)
    C                  Where C and F are the temperature in degrees
            9              Celsius and Fahrenheit respectively.


2.4 Use Formulas to Solve Word Problems
Example: Find the markup on a CD          Example: After expenses of $55.15
player whose wholesale cost is $219       were paid, a Rotary Club donated
and whose retail price is $395.           $875.85 in proceeds from a pancake
                                          breakfast to a local health clinic.
                                          How much did the breakfast gross?




2.4 Use Formulas to Solve Word Problems
Example: Cryobiologists freeze living matter to preserve it for future use.
They can work with temperatures as low as 270 C. Change this to
degrees Fahrenheit.




2.4 Use Formulas to Solve Word Problems
Example: Three years after opening an account that paid 6.45% annually,
a depositor withdrew the $3,483 in interest earned. How much money was
left in the account?




2.4 Use Formulas to Solve Word Problems
Example: Rose Parade floats travel down the 5.5 mile-long parade route at
a rate of 2.5 miles per hour. How long will it take a float to complete the
parade if there are no delays?




2.4 Use Formulas to Solve Word Problems
                       Geometry Formulas to Know




           Rectangle                          Rectangular Box
  Perimeter = sum of all sides               Volume  l  w  h    in 3
                                                                  units
               or             in
                             units
     Perimeter  2l  2w

                          in 2
        Area = l  w     units


2.4 Use Formulas to Solve Word Problems
                         Geometry Formulas to Know




             Triangle                           Parallelogram             in
                                                                         units
  Perimeter = sum of all sides            Perimeter = sum of all sides

           Area =   1
                    2   bh                           Area  bh
    in 2
   units

                                           For these formulas:
                                            The height meets
                                            the base-side at a
                                             90-degree angle

2.4 Use Formulas to Solve Word Problems
                    Geometry Formulas to Know




           Trapezoid                              Circle              in
                                                                     units
  Perimeter = sum of all sides            Circumference   d
                   a+b
        Area = h                               Area   r 2
                    2
                                                        3.14159...
                                                          227
                                                   *To minimize rounding-
                                                    errors we will use the
                                                     button on our TI

2.4 Use Formulas to Solve Word Problems
                         Geometry Formulas to Know


                  base




              Pyramid
                                                      Cone
           Volume  hB   1   *

                                                Volume  1  r 2 h
                         3
    *                                                    3
        B is the area of the base




2.4 Use Formulas to Solve Word Problems
                    Geometry Formulas to Know




              Sphere                            Cylinder
          Volume  4  r 3
                   3                        Volume   r 2 h




2.4 Use Formulas to Solve Word Problems
Example: For each of the following scenarios, indicate which geometric
concept (perimeter, circumference, area or volume) should be used and
which unit of measurement (units, units 2 , units 3 ) would be appropriate.

• The amount of storage in a freezer



• The distance around the outside of a building lot



• The amount of land making up the Sahara Desert



• How far a bike tire rolls in one revolution



2.4 Use Formulas to Solve Word Problems
Example: A horse trots in a perfect       Example: Find the perimeter and
circle around its trainer at the end of   area of the truss below:
a 28 foot-long rope. How far does
the horse travel as it circles the




                                                          6 ft
trainer once? (Round your answer to
the nearest tenth.)                                      16 ft


                                          perimeter:




                                          area:




2.4 Use Formulas to Solve Word Problems
Example: Find the amount of space         Example: Find the exact area of the
in the hamster tube below. Round          square road sign below:
your answer to the nearest tenth.
              12 in




                               3 in




2.4 Use Formulas to Solve Word Problems
Example: Find the volume of a spherical-shaped pumpkin that has a
diameter of 9 inches. Round your answer to the nearest hundredth.




2.4 Use Formulas to Solve Word Problems
                            Solving Linear Equations in One Variable:
                                1. If the equation contains fractions, multiply both sides by the
                                   magic number (LCM of the denominators) to clear fractions
                                2. Use the Distributive Property to remove the parentheses
“undoing” the operations:
  Isolate the variable by




                                   (then combine the like-terms on each side of the equation)
                                3. Use the Addition and Subtraction Properties to get all of the


                            {      variables on one side of the equation together
                                   (and all of the numbers on the other side of the equation)
                                4. Use the Multiplication and Division Properties to make the
                                   coefficient of the variable equal to 1


                                   Remember that solving an equation means that we
                                         isolate the variable we are solving for!


2.4 Solve a Formula for a Given Variable
Example: Solve each formula for the given variable.

         d  rt for t                           I  prt for r




2.4 Solve a Formula for a Given Variable
Example: Solve each formula for the given variable.

      P  2l  2w for l                       K  1 mv 2 for m
                                                  2




2.4 Solve a Formula for a Given Variable
Example: Solve each formula for the given variable.
     5 y  25  x for y                        6 y  12  5x for y




                                            We will need to
                                           have this skill for
                                           chapters 3 and 7.


2.4 Solve a Formula for a Given Variable
Independent Practice
  You learn math by doing math. The best way to learn math is to practice,
  practice, practice. The assigned homework examples provide you with an
  opportunity to practice. Be sure to complete every assigned problem (or more
  if you need additional practice). Check your answers to the odd-numbered
  problems in the back of the text to see whether you have correctly solved each
  problem; rework all problems that are incorrect.

Read pp.149-157

Homework: pp.157-162 #1, 2, 3, 5, 8, 11, 15-23 odds, 27, 31, 33,
                     37-51 odds, 65, 67, 69, 73, 75, 79, 83, 85,
                     91, 95(hint: it’s a half-sphere), 103, 105




2.4 Formulas

				
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