Wang made a rectangle with a 24-meter belt. Because one side is a wall, it is only surrounded by three sides, two of which are close to the wall and the other is parallel to the wall. If we set the length of the side near the wall to x, the enclosed area is:

s= 1/2*(2x*(24-2x))

For 2x*(24-2x), when 2x=24-2x, the maximum value is obtained, 2x = 24-2xx = 6 6 * (24-2 * 6) = 72.

There is a law in primary school mathematics: when the sum of two non-negative numbers is a certain value, the product is the largest when the two numbers are equal.

This is because: (a+b)*(a-b)=a*a-b*b Therefore, a*a is not less than a+b)*(a-b).