2.1 Constructing expressions

• Math
• Secondary Education

2.1 Constructing expressions

WALT:  use letters to represent numbers

use the correct order of operations in algebraic expressions

write and use expressions.

WILF: I can understand that the order of operations rules apply to algebra.

 I can use these rules to write algebraic terms and expressions.

I can read an expression written in words and convert it to an expression written in algebraic terms, and vice versa.

 

2.1 Constructing expressions

In algebra you can use a letter to represent an unknown number. 

An expression contains numbers and letters, but not an equals sign. 

An equation contains numbers and letters and an equals sign.

Example: 

5n + 4 = 19 is an equation.

5n + 4 is an expression.

Sort  the expressions and oequations.

Expressions

Equations

4x+9

-9ab

6(m+3)=10

4n=8

3/4a

5a+6b-4c

y=mx+b

P=2(l+w)

2.1 Constructing expressions

• coefficient - a number in front of a variable in an algebraic expression 
• term - a single number or variable, or numbers and variables multiplied together

• constant - a number on its own (with no variable)
• variable - a symbol, usually a letter, that can represent any one of a set of values

Label the parts of the expression.

-

Coefficients

terms

variables

constant

Words and Phrases to Math Symbols

Addition

Subtraction

Multiplication

Division

Equal

Plus

Increased By

Altogether

More Than

Total of

Take Away

Less 

Less Than

Fewer Than

Difference

Triple

Increased By a Factor

Product

Of

Multiple

Quotient of

Divisor

Per

Ratio of

Split Up

is

was

the same as

Yields

Will be

Maliha thinks of a number, y.

Write an expression for the number Maliha gets when she:

multiplies the number by 2

divides the number by 2

multiplies the number by 4, then adds 3

multiplies the number by 2, then subtracts 5

multiplies the number by 2, then subtracts the result from 5

divides the number by 4, then adds 3

2y

4y + 3

2y − 5

5 − 2y

Write an expression for each of these.

1) x more than y
2) x less than y
3) m more than two times n

4) a less than three times b

5) p multiplied by q

6) four times g multiplied by h

Write an expression for each of these
a) I think of a number x. I multiply the number by 6, then add 1.
b) I think of a number x. I multiply the number by 4, then subtract 9.
c) I think of a number x. I divide the number by 6, then subtract 1.
d) I think of a number x. I divide the number by 2, then add 7.
e) think of a number x. I multiply the number by 2, then subtract the result from 25.

Write an expression for each of these situations. You can choose your own letters, but make sure that you explain what your letters represent.
a) the total cost of two tacos and four burritos
b) the total cost of eight lemon cakes and five carrot cakes
c) the total value of six gold coins is doubled
d) the total value of five silver coins is tripled