Application: Perimeter of a Rectangle
The perimeter of a rectangle is found by evaluating the algebraic expression P = 2l + 2w, where l is the length and w is the width. For a rectangle with l = 5 and w = 3: P = 2(5) + 2(3) = 10 + 6 = 16. Following the order of operations, multiplication comes before addition. For l = 7.5 and w = 4: P = 15 + 8 = 23. This applied algebra skill from Reveal Math, Course 1, Module 5 connects multi-variable expression evaluation to real-world geometry in 6th grade.
Key Concepts
The perimeter of a rectangle can be calculated by evaluating the algebraic expression: $$P = 2l + 2w$$ where $l$ represents the length and $w$ represents the width of the rectangle.
Common Questions
What is the formula for the perimeter of a rectangle?
P = 2l + 2w, where l is the length and w is the width. Multiply each dimension by 2 and add the results.
How do I evaluate a perimeter expression?
Substitute the values for l and w, then follow order of operations: perform multiplication first (2l and 2w), then add the two products.
Find the perimeter of a rectangle with length 8 and width 3.
P = 2(8) + 2(3) = 16 + 6 = 22 units.
Why does the perimeter formula have two separate terms instead of one?
The two terms represent the two pairs of parallel sides. 2l covers the two long sides and 2w covers the two short sides.
How is evaluating a perimeter expression different from just calculating perimeter?
Evaluating the expression 2l + 2w requires substituting variable values and following order of operations, which is an algebraic skill beyond basic arithmetic.
When do 6th graders apply the perimeter formula as an algebra expression?
Module 5 of Reveal Math, Course 1 uses the perimeter formula as an application of evaluating multi-variable algebraic expressions.