# Retail Math Formulas by cch21045

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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
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
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:
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.