C2.2 Evaluating Algebraic Expressions that Involve Whole Numbers.
Skill: Evaluating Algebraic Expressions Involving Natural Numbers
To evaluate an algebraic expression, variables are replaced with numerical values and calculations are performed according to the order of operations.
When students work with formulas, they are evaluating expressions.
Substituting variables with numerical values often requires the use of parentheses. For example, the expression 4c becomes 4(c) then 4 (5) when c = 5. The operation between 4 and 5 is understood to be a multiplication.
Source: Ontario Curriculum, Mathematics Curriculum, Grades 1-8, 2020, Ontario Ministry of Education.
Example 1
Evaluate the algebraic expression below, knowing that a = 25.
2a + 200
= 2 (25) + 200
= 50 + 200
= 250
Example 2
The base of a rectangle is 3 decimeters and its height is 4 decimeters. What is its area?
b × h
= 3 × 4
= 12
The area of the rectangle is 12 dm2.