Expressions and Formulas Expressions and Formulas

1) order of operations2) variable3) algebraic expression4) formula

Use the order of operations to evaluate expressions. Use Formulas.

Nurses setting up intravenous or IV fluids must control the flow rate F, in drops perminute.

They use the formula , where V is the volume of the solution in

milliliters, d is the drop factor in drops per milliliter, and t is the time in minutes.

t

dVF

x

Suppose a doctor orders 1500 milliliters of IV saline to be given over 12 hours.

Using the drop factor of 15 drops per milliliter, the expression

gives the correct flow rate for this patient’s IV.

60 x 12

15 x 1500

Expressions and Formulas Expressions and Formulas

A numerical expression such as must have exactly one value. 60 x 12

15 x 1500

In order to find that value, you must follow the _________________.

Some students remember the order by using the following mnemonic:

PEMDAS

lease

xcuse

y

ear

unt

ally

(parentheses / grouping symbols)

(exponents)

(multiplication – from left to right)

(division – from left to right)

(addition – from left to right)

(subtraction – from left to right)

order of operations

Expressions and Formulas Expressions and Formulas

Find the value of 5]3)410(2[ 2 = [2(6)2 + 3] ÷ 5

= [2(36) + 3] ÷ 5

= [72 + 3] ÷ 5

= [75] ÷ 5

= 15

Expressions and Formulas Expressions and Formulas

Find the value of

3

2

6

2 52 12 2

Expressions and Formulas Expressions and Formulas

_________ are symbols, usually letters, used to represent unknown quantities.Variables

Expressions that contain at least one variable are called algebraic expressions.

You can evaluate an algebraic expression by replacing each variable with a numberand then applying the order of operations.

Evaluate the expression ( x – y )2 – 2wz, if w = 6, x = 0.4, y = , and z = – 3. 2

1

( x – y )2 – 2wz = ( 0.4 – )2 – 2(6)( -3 )2

1

= ( – 0.1)2 – 12(– 3)

= ( 0.01) + 36

= 36.01

Expressions and Formulas Expressions and Formulas

A _______ is a mathematical sentence that expresses the relationship between certain quantities.

formula

If you know the value of every variable in the formula except one, you can find thevalue of the remaining variable.

14 in

26 in

6 inThis shape is called a _________.trapezoid

The formula for calculating the area of a trapezoid is 212

1bbhA

Expressions and Formulas Expressions and Formulas

14 in

26 in

6 in

Find the area of the trapezoid:

212

1bbhA ininin 2614)6(

2

1

inin 40)6(2

1

inin 40)3(

2120in

The area of the trapezoid is 120 square inches.

Expressions and Formulas Expressions and Formulas

Find the value of

3

2

6

2 52 12 2

Expressions and Formulas Expressions and Formulas

Expressions and Formulas Expressions and Formulas