7th Grade Math

34 Expressions and Patterns

In algebra, the multiplication sign is often omitted.

The numerical factor of a multiplication expression that contains a

variable is called a coefficient. So, 6 is the coefficient of 6d.

Evaluate Expressions

Evaluate 8w - 2 v if w = 5 and v = 3.

8 w - 2 v = 8 ( 5 ) - 2 ( 3 ) Replace w with 5 and v with 3.

= 40 - 6 Do all multiplications first.

= 34 Subtract 6 from 40.

Evaluate 4 y^2 + 2 if y = 3.

4 y 2 + 2 = 4 ( 3 ) 2 + 2 Replace y with 3.

= 4 ( 9 ) + 2 Evaluate the power.

= 38 Multiply, then add.

Evaluate each expression if a = 4 and b = 3.

d. 9 a - 6 b e. _ab 2 f. 2 a 2 + 5

The fraction bar is a grouping symbol. Evaluate the expressions in the

numerator and denominator separately before dividing.

HEALTH Use the formula at the left to find Latrina’s minimum

training heart rate if she is 15 years old.

3(220 - a)

_ 5 =

3(220 - 15 )

_ 5 Replace a with 15.

=

3(205)

_ 5 Subtract 15 from 220.

= _^6155 Multiply 3 and 205.

= 123 Divide 615 by 5.

Latrina’s minimum training heart rate is 123 beats per minute.

g. MEASUREMENT To find the area of a triangle, use the formula _bh

2

,

where b is the base and h is the height. What is the area in

square inches of a triangle with a height of 6 inches and base of

8 inches?

Real-World Link

Athletic trainers use the

formula _ 3(220 5 -^ a) ,

where a is a person’s

age, to find their

minimum training

heart rate.

RRR

A

6 times d 9 times s times t m times n

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