Although the title in the statement is not detailed, it may contain two meanings:

1, there is a diagram but it is not drawn, and the diagram is limited to a rectangle or a square;

2. How to surround, the bigger the area, the better;

Grade four pupils should understand or master a basic principle:

When the perimeter is fixed, the square area is the largest among all rectangles that meet the conditions.

It is conceivable that on the other side of the wall, there is also a 50-meter fence, which together looks like a big rectangle; The largest area on each side means the largest area on the whole. (You can draw a picture yourself)

Conversely, when the overall area is the largest, the area of each side is also the largest.

When is the whole area the largest? It is the principle mentioned above: together it is a square;

Therefore:

The wall divides this square table into two halves, one side is rectangular, twice as long and twice as wide;

Pupils can answer with "and times questions";

The width is 1 and the length is 2. Because the long side is against the wall, only three sides of the rectangle have fences. The fence is:

1× 2+2 = 4 (copies); 4 copies * * * 50m, so each copy is: 50÷ 4 = 12.5 (m), which is the width;

The length is twice the width, and the length is: 12.5× 2 = 25 (meters).

The flower bed area is 25× 12.5 = 3 12.5 (m2).