Explanation:

- The perimeter of a square is calculated as the sum of all its sides. Since a square has four equal sides, its perimeter is 4 times the length of one side.

- Half of the perimeter is given as 50 cm. Therefore, the full perimeter is 50 cm * 2 = 100 cm.

- To find the length of each side, divide the full perimeter (100 cm) by 4.

- So, 100 cm / 4 = 25 cm.

- This means each side of the square is 25 cm long.

Option 3: 25 cm - This is the correct answer.