Find the area of the rectangle if it is known that 1/5 of the rectangle is 8 cm2.

This problem can be solved in different ways. One of the simplest and most versatile is the proportion solution.

From the condition it is known that 1/5 of the area of the rectangle is 8 cm 2. Then let 100% (or 1) of the area of the rectangle be x cm 2. Based on these data, we will compose the proportion:

1/5 is 8 cm 2;
1 is x cm 2.

Using the main property of proportion, we express and define what x is equal to:

x = 8 * 1: 1/5 = 8 * 5/1 = 8 * 5 = 40 (cm 2).

Answer: the area of the rectangle is 40 cm 2.