M60 D10

3.1 Working with Formulas3.2 Formulas in Geometry

Warm-up

Solve each of the following linear equations.

1.

2.

3.

9 3 5 9x x

6 3 3 2x x

2 3

3 3 4 2

x x x

Lesson 3.1

Working with Formulas

Formulas

Formulas are general rules or principles stated mathematically.

Caution: Capital letter variables are generally different (values) than lower case variables.

Evaluating Formulas

When given all but one value within a formula we are able to substitute the given values and solve for the unknown.

We can either substitute into the formula as given or rearrange the formula to isolate the unknown variable.

Simple Interest

I=PrtA savings account of $3500 is left for 9 months

and draws simple interest at a rate of 7%. A) how much interest is earned? B) what is the balance in the account at the end of the 9 months? (time (t) is in years)

Solving for Different Variables

Distance formula: d=rt

• Solved for “d” in terms of “r” and “t”

• Solve for “t” in terms of “d” and “r”

Solving for Different Variables

• Temperature conversion:

• Solve for “C” in terms of “F”

932

5F C

Cost

Total cost “C” of producing “x” items can be found by the formula:

where “a” is the cost per item and “k” is the fixed costs (rent, utilities, and so on).

C ax k

Cost

• The total cost to produce 80 dolls is $1097.50. If each doll costs $9.50/each to produce, find the fixed costs.

• Solve for k in terms of C and a

C ax k

Hawkes Example

, solve for m2

m nA

2 , solve for bP a b

, solve for xy mx b

3 12, solve for x

8

xR

Lesson 3.2

Formulas in Geometry

Geometry Vocabulary

Area

Hawkes Practice

Volume

Find the width of a cereal box with volume 1260 cm3 if its length is 14 cm and its height is 20 cm.V=lwh

Coming up…

• Mid-term grades calculated this Friday• Quiz #4 Due Friday November 1st

• Test #2 Due November 15th

• Day 11 Reading Guide 3.3

Exit Ticket

1. Solve for the given variable:

2. Solve for the given variable:

3. The perimeter of a square is 10 2/3 meters. Find the length of the sides.

; solve for V lwh h

2 5; solve for x y x