Each side of the rectangle was enlarged by 3 cm, as a result of which its area increased by 39 cm2.

Each side of the rectangle was enlarged by 3 cm, as a result of which its area increased by 39 cm2. Find the perimeter of the original rectangle.

Let’s denote the sides X and Y, we get the equation: X * Y + 39 = (X + 3) (Y + 3) <=> (Expand the brackets) XY + 39 = XY + 3X + 3Y + 9 <=> (Move the unknowns to the left known to the right) XY-XY-3X-3Y = 9-39 <=> (Transform similar terms) -3X-3Y = -30 <=> (Divide by -3) X + Y = 10. The perimeter is equal to twice the sum of the sides => P = 2 (X + Y) => P = 2 * 10 => p = 20 cm.