SME
Grade 4 Math · Measurement & Data
Use perimeter and area formulas
Use this for “A garden is 9 m long and 4 m wide. Find its area and its perimeter.”
Diagram
This is an example. Type your own values to start a new problem.
Length
example
Width
example
Area
calculated
Half the perimeter
worked out (not typed)
Perimeter
calculated
Formulas
9 × 4 = 36
Length × width = area
9 + 4 = 13
Length + width = half the perimeter
2 × 13 = 26
2 × (length + width) = perimeter
Assumptions
•
Area is the space inside: length × width, in square units.
•
Perimeter is the distance around: two lengths and two widths, so 2 × (length + width).
•
From the perimeter, half of it is length + width. Take away the side you know to find the other.
•
Whole-number sides up to 100.
Step-by-step
WE KNOW
Length: 9 m
Width: 4 m
FIND
area, half the perimeter, perimeter
Step 1 · Find area
9 × 4 = ?
Length × width = area
Multiply the length by the width: rows of unit squares.
Area = 36 m²
Step 2 · Find half the perimeter
9 + 4 = ?
Length + width = half the perimeter
One length and one width: half of the way around.
Half the perimeter = 13 m
Step 3 · Find perimeter
2 × 13 = ?
2 × (length + width) = perimeter
The perimeter is two lengths and two widths: double the half perimeter.
2 × 13 = 26
Perimeter = 26 m
Check
Put the numbers back in. Both sides should match.
9 × 4 = 36 ✓
9 + 4 = 13 ✓
2 × 13 = 26 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.