一根长 210 cm 的铁丝被剪成 2 段，分别弯成了一个长方形和一个正方形。长方形的长是 48.5 cm，宽是 38.5 cm。求正方形的边长。 答：___ cm

1. Calculate the perimeter of the rectangle.

The length of the rectangle is $48.5\text{ cm}$ and its breadth is $38.5\text{ cm}$.
$\text{Perimeter of rectangle} = 2 \times (48.5 + 38.5) = 2 \times 87 = 174\text{ cm}$

2. Calculate the perimeter of the square.

The total length of the wire is $210\text{ cm}$.
$\text{Perimeter of square} = 210 - 174 = 36\text{ cm}$

3. Calculate the length of one side of the square.

Since a square has 4 equal sides:
$\text{Side of square} = 36 \div 4 = 9\text{ cm}$