Given: Length of the rectangle increased by = 80% Breadth of the rectangle increased by = 20% Formula: Area of the rectangle = Length × Breadth Calculation: Let length and breadth of the rectangle be x and y respectively ⇒ Area of the rectangle = xy New length of the rectangle = x × (180/100) = 1.8x New breadth of the rectangle = y × (120/100) = 1.2y ⇒ New area of the rectangle = 1.8x × 1.2y = 2.16xy Area increased by = 2.16xy – xy = 1.16xy ∴ required percent = (1.16xy/xy) × 100 = 116% Short Trick: If length and breadth increased by 80% and 20% respectively ⇒ Area increased by = 80 + 20 + (80 × 20)/100 = 100 + 16 = 116%