Algebraic Expression Grade 8 Instructions.pptx

In this lesson you will learn about
the following:
• Algebraic expression and its parts
• Writing an algebraic expression
• Simplifying algebraic expressions
• Evaluating algebraic expressions
Learning
Outcomes
This template uses the math equations tool.
To access, go to Canva apps and search for ‘equations’
or select any expression or equation on the template
and click ‘edit’ on the toolbar.

A fruit shake stand prepares 3 boxes of
mangoes every day.
All the boxes have an equal
number of mangoes.
What expression can we
use to find out the number
of mangoes in each box?

EXAMPLE
What is an Algebraic Expression?
An algebraic expression is a mathematical
expression with constants, variables and operations.

Parts of algebraic expression:
Constant - is a fixed value
in an expression
Variable - is a letter that
is used to represent an
unknown value
Coefficient - is a constant
multiplier of a variable
Term - is a constant, a
variable, or a coefficient
and variable multiplied
together
coefficient variable constant
term term

Writing Algebraic Expressions
What do we
know?
We know that there are
3 boxes. This means
that 3 is a constant.
What is the
unknown
value?
We do not know the
number of mangoes in
each box.
3
2
1
STEP 1 STEP 2
Going back to our problem, let’s represent the total
number of mangoes as an algebraic expression.

Represent the
unknown with
a variable.
Let = the number
of mangoes per box
Choose the
operation to use.
To get the total number of
mangoes, we multiply the
number of boxes by the
number of mangoes in each
box.
STEP 3 STEP 4

Write the
expression.
The algebraic expression for
the total number of mangoes
is:
STEP 5
Note that we can also use the
operation addition, which means that

Expanded Expression Simplified Expression
Take a look at how operations are used to write algebraic
expressions.

Simplifying Algebraic Expressions
Remember the following rules when simplifying algebraic expressions:
Unlike terms
Terms with the same
variable and power can be
combined by addition or
subtraction.
Like terms
Terms with different
variables or different power
cannot be combined by
addition or subtraction.

At a food stall, for every cup of avocado
shake, 2 avocados are needed, and for
every avocado toast, 1 avocado is needed.
Write the algebraic expression for the
total number of avocados needed for
shakes and toasts bought.
Try this!

Solution and Answer:
What do we know?
2 avocados per cup,
1 avocado per toast.
=
=
What are the
unknown values?
Number of cups and
number of toasts.
Represent the
unknowns with
variables.
number of cups
number of toasts
STEP 1 STEP 2 STEP 3

Solution and Answer:
Choose the operation.
Multiplication and addition.
Write the expression.
STEP 4 STEP 5
Total number
of avocados
ANSWER
+
Note that

Evaluating Algebraic Expressions
What if a student buys 4 avocado shakes and 2
toasts.
Using the algebraic expression, how many
avocados would be needed for the student’s order?

Let’s visualise! The student bought 4 cups of avocado shakes and 2 toasts.
4 cups of avocado shakes =
8 avocados
2 avocado toasts =
2 avocados
Remember that:
By adding the number of avocados, we can say that we
need 10 avocados for 4 shakes and 2 toasts.
ANSWER
=
=
+

In evaluating algebraic expressions, we can use substitution!
What do we know? Substitute the values.
Total number of avocados
Total number of avocados
where
number of cups
number of toasts
Student bought 4 cups of avocado
shakes and 2 avocado toasts.
This means that,
STEP 1 STEP 2
We got the same answer,
which is 10 avocados.
ANSWER

If is the cost of a cookie,
write the algebraic
expression for the cost of a
waffle.
A B
A waffle costs £1 more than three
times a cookie.
Try this!
If the cookie costs £2, how
much is the waffle?

If is the cost of cookie,
write the algebraic
expression for the cost of a
waffle.
Cost of waffle Cost of waffle
A B
ANSWER ANSWER
A waffle costs £1 more than three
times a cookie.
Try this!
The waffle costs £7.
If the cookie costs £2, how
much is the waffle?

Summary
Constant - is a fixed value in an
expression
Variable - is a letter that is used to
represent an unknown value
Coefficient - is a constant multiplier of a
variable
Term - is a constant, a variable, or a
constant and variable multiplied
together
coefficient variable constant
term term
An algebraic expression
is a mathematical expression
with constants, variables,
and operations.

Summary
Building Algebraic Expressions
What is known?
What is known?
What is the unknown?
Substitute the known values.
Choose the operation.
Represent the unknown with a variable.
Write the expression.
Simplifying Expressions
Terms with the same variable can be
combined by addition or subtraction.
Terms with different variables cannot be
combined by addition or subtraction.
STEP 1
STEP 1
STEP 2
STEP 2
STEP 4
STEP 3
STEP 5

Think about it!
Let be the measurements of
the sides of a fruit shake stall
with a square-shaped base.
What is the algebraic
expression that represents
its area?
Share your answer in our next
session.

Reference
Mathspace. "Build algebraic expressions I| Year 7-9 Math |
UK Secondary (7-11)." Accessed 26 January 2024,
https://mathspace.co/textbooks/syllabuses/Syllabus-453/topics/
Topic-8409/subtopics/Subtopic-111287/

Text
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Algebraic Expression Grade 8 Instructions.pptx

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