3. The area of the rectangle is equal to the area of a square with a perimeter of $36 \mathrm{~cm}$. Which has a larger perimeter and by how much, if the length of one side of the rectangle is equal to $27 \mathrm{~cm}$.
Solution. Since the perimeter of the square is $36 \mathrm{~cm}$, its side is equal to $36: 4=9 \mathrm{~cm}$, and its area is equal to $9.9=81 \mathrm{~cm}^{2}$. The area of the rectangle is also $81 \mathrm{~cm}^{2}$, and since one of its sides is equal to $27 \mathrm{~cm}$, we get that the other side of the rectangle is equal to $81: 27=3 \mathrm{~cm}$. The perimeter of the rectangle is equal to $2 \cdot 27+2 \cdot 3=60 \mathrm{~cm}$. The perimeter of the rectangle is $24 \mathrm{~cm}$ larger than the perimeter of the square.