The area of a rectangle is thrice that of a square. If the length of the rectangle is 40 cm and its breadth is 3/2 times that of the side pf the square, then the side if the square is :

Answer: Option B

Let the side of the square be x cm
Then, its area = x² cm²
Area of the rectangle = 3x² cm²
∴ 40 × $$\frac{3}{2}$$ × x = 3x²
⇔ x = 20 cm