The length of rectangle is thrice the side of square. Difference between perimeter of rectangle and square is 40 cm. If breadth of rectangle is 8 cm, then find area of square?

Lets length of rectangle is 3x meters and side of square x meters

2(3x + 8) – 4x = 40

6x + 16 – 4x = 40

2x = 24 ⇒ x = 12 cm

Area of square = a²

Area of square = 12² = 144 cm²