Download : a symbol, usually a letter that represents one or more numbers. Any

8th Grade
Mathematics
Unit: 02 Lesson: 02
: a symbol, usually a letter that represents one or more numbers. Any letter may be used as
a variable, but some letters can be confused for numbers, for example the letter “S” and “5” and the
letter “Z” and “2”.
: consists of numbers, variables, and operations
To
a mathematical expression, substitute a given numeric value in for the variable(s) and
perform the given mathematical operation(s) using the correct order of operations.
Many words and phrases suggest mathematical operations.
Examples:
plus, the sum of, increased by, total, more than, added to
minus, the difference of, decreased by, fewer than, less than, subtracted from
times, the product of, multiplied by, twice
divided by, the quotient of, separate into equal parts
Examples:
the sum of a number and 10
the difference of a number and 21
the product of 6 and a number
- 21
6
48
the quotient of 48 and a number
1
4
one fourth of a number
x
+ 10
Order is important when translating subtraction and division expressions.
The
of a number and 6 is represented by – 6, not 6 – . Four less than a
number is represented by – 4 since it implies you have a number first then take four from
it.
10
The
of a number and ten is represented by ÷ 10 or
, not 10 ÷ or
10
When representing multiplying a number and a variable, the number is written first followed by
the variable. For example, the product of and 3 would be written 3 .
x
©2010, TESCCC
08/01/10
8th Grade
Mathematics
Unit: 02 Lesson: 02
Expressions can be evaluated by substituting given values for the variables and using the correct
order of operations.
Examples:
1. Evaluate the variable expression 3 - 5 , if
x
Substitute 7 for
a. 8
c.
( – 3)
(í9)(6.2 – 3)
= (í28.8)
2
6(í9)2
6(81)
= 486
©2010, TESCCC
= 6.2 and
(6.2) (í 9)
= (í55.8)
8(6.2)
= 49.6
d. 6
e.
= 4.
2. Evaluate the each expression below if
= 7 and
and 4 for . Put substituted values in parentheses.
3(7) – 5(4)
Simplify the resulting expression using order of operations.
3(7) – 5(4)
= 21 – 5(4)
= 21 – 20
=1
x
b.
1
2
2
3
1
2
(6.2) – (í9)
2
3
2
= 3.1 – (í9)
3
= 3.1 – (í6)
= 3.1 + 6
= 9.1
08/01/10
= (í 9).