Question 679427
You should write rectangles like

10 cm x 10 cm to get a perimeter of 40 cm, and the area is 100 sq. cm.
15 cm x 5 cm to get a perimeter of 40 cm, and the area is 75 sq. cm.
19 cm x 1 cm to get a perimeter of 40 cm, and the area is 19 sq. cm.

There are many possibilities.