Mathematical Reasoning
A rectangle has a perimeter of 40 cm.
Question 1 · Multiple choice
Question
A rectangle has a perimeter of 40 cm.
Its length is 4 times its width.
Options
What is the area of the rectangle?
- A.24 cm²
- B.64 cm²
- C.40 cm²
- D.48 cm²
- E.96 cm²
Correct answer
Explanation
Step 1: Set up the dimensions using one variable
Let the width = w cm.
The length is 4 times the width: length = 4w cm.
┌──────────────────────────┐
│ │ w
│ length = 4w │
└──────────────────────────┘
←──────── 4w ────────────→
Step 2: Use the perimeter formula
Perimeter = 2 × (length + width)
40 = 2 × (4w + w)
40 = 2 × 5w
40 = 10w
w = 40 ÷ 10 = 4 cm
Step 3: Find the length
Length = 4w = 4 × 4 = 16 cm
Step 4: Calculate the area
Area = length × width = 16 × 4 = 64 cm²
Check perimeter: 2 × (16 + 4) = 2 × 20 = 40 cm ✓
Answer: 64 cm²