Length = 10 feet, Width = 7 feet
P = 2 × (length + width)
P = 2 × (10 + 7)
P = 2 × 17 = 34 feet
Area = side × side = 9 × 9 = 81 square meters
Plants per square meter = 4
Total plants = 81 × 4 = 324 plants
Length = 8 cm, Width = 5 cm
Perimeter = 2×(8+5) = 26 cm
Area = 8×5 = 40 cm²
Length = 3×8 = 24 cm, Width = 5 cm
Perimeter = 2×(24+5) = 58 cm
Area = 24×5 = 120 cm²
Perimeter ratio: 58÷26 ≈ 2.23 (about 2.23 times larger)
Area ratio: 120÷40 = 3 (exactly 3 times larger)
Perimeter: The total distance around the outside of a shape. For rectangles, P = 2×(length + width)
- Identify length and width: 10 ft and 7 ft
- Add the length and width: 10 + 7 = 17
- Multiply by 2: 2 × 17 = 34 ft
Perimeter is always measured in linear units (ft, cm, m)
The perimeter of the room is 34 feet.
Area: The amount of space inside a 2D shape. For squares, A = side × side
- Calculate area: 9 × 9 = 81 square meters
- Multiply by plants per square meter: 81 × 4 = 324 plants
Area is always measured in square units (ft², cm², m²)
The area is 81 square meters, and 324 plants can fit in the garden.
Multiplicative comparison: Comparing quantities using multiplication (times larger)
- Calculate Rectangle A: P = 26 cm, A = 40 cm²
- Calculate Rectangle B: Length = 3×8=24 cm, P = 58 cm, A = 120 cm²
- Compare: P ratio ≈ 2.23, A ratio = 3
When one dimension is multiplied by n, area changes by factor n, but perimeter changes differently
Rectangle B has a perimeter about 2.23 times larger and an area exactly 3 times larger than Rectangle A.
Definition: The total distance around the outside of a shape.
Formula (Rectangle): P = 2 × (length + width)
Formula (Square): P = 4 × side
Units: Linear measurements (cm, m, ft, in)
Definition: The amount of space inside a 2D shape.
Formula (Rectangle): A = length × width
Formula (Square): A = side × side
Units: Square measurements (cm², m², ft², in²)
Definition: Comparing quantities using multiplication.
Example: "3 times larger" means multiply by 3.
Method: Divide larger quantity by smaller to find ratio.
- Identify the shape: Rectangle, square, or composite figure
- Find all dimensions: Measure or identify given lengths
- Select the formula: P = 2(l+w) for rectangles, P = 4s for squares
- Substitute values: Replace variables with known numbers
- Calculate: Perform the arithmetic operations
- Label: Include correct linear units
- Identify the shape: Rectangle, square, or composite figure
- Find dimensions: Length and width (or base and height)
- Select the formula: A = l×w for rectangles, A = s² for squares
- Substitute values: Replace variables with known numbers
- Calculate: Perform the multiplication
- Label: Include correct square units
- Identify the quantities: Find the two values being compared
- Determine the relationship: Which is larger? By what factor?
- Set up the equation: Larger = Factor × Smaller
- Solve for the unknown: Use division or multiplication as needed
- Verify: Check that your answer makes sense