The perimeter of a square is 14 cm. If each side of the square is increased by x cm, its area increases by 120 cm². What is the value of x?

Correct option is B

Given:

Perimeter of square = 14 cm
Increase in area = 120 cm²

Formula used:
Perimeter of square = 4 × side
Area of square = side²

Solution:
Side = 14 ÷ 4 = 3.5 cm

Let increase in each side = x cm

New side = 3.5 + x

New area = (3.5 + x)²

Old area = 3.5² = 12.25

Increase in area = (3.5 + x)² – 12.25 = 120

(3.5 + x)² = 132.25

3.5 + x =$$\sqrt{132.25}$$​ = 11.5

x = 11.5 – 3.5 = 8