The side of a 10 m long square was reduced by 10%. How many percent has the perimeter of the square decreased?

Let’s calculate the perimeter of the square before decreasing. Let’s multiply its side to decrease – 10 meters by 4:

4 * 10 = 40 meters.

The perimeter of the square before reduction is 40 meters.

Let’s calculate the length of the side of the square after decreasing.

10 * 0.9 = 9 meters.

After reduction, the length of the side of the square became 9 meters

Let’s calculate the perimeter of the square after reducing its side:

9 * 4 = 36 meters.

40 – 36 = 4 meters.

40 -100%,

4 – x%.

x = 4 * 100: 40 = 10%.

Answer: after reducing the side by 10%, the perimeter of the square has decreased by 10%.