Answer:
The perimeter of the rectangle is 70 cm
Explanation:
Let us use the ratio method to solve the question
∵ Two sides of a rectangle are in the ratio 3 : 4
→ Let the width is the shorter side and the length is the longer side
∴ The ratio between the width and the length is 3 : 4
∵ The longer side is 20 cm
∴ The length of the rectangle = 20 cm
→ By using the ratio method
→ width : length
→ 3 : 4
→ w : 20
→ By using cross multiplication
∵ w × 4 = 3 × 20
∴ 4w = 60
→ Divide both sides by 4
∴ w = 15
∴ The width of the rectangle = 15 cm
∵ The perimeter of the rectangle = 2(length + width)
∴ The perimeter of the rectangle = 2(20 + 15)
∴ The perimeter of the rectangle = 2(35)
∴ The perimeter of the rectangle = 70 cm
∴ The perimeter of the rectangle is 70 cm