The rectangle is 8 cm long and 40% wide. Find the perimeter of the rectangle.

We will analyze this problem. And so, the perimeter can be found as the length add the width and all this is still multiplied by two, that is, P = 2 (a + b). We know the length and it is equal to 8 cm, and the width is 40% of the length. Well, first we need to find the width of the rectangle, and then the perimeter itself. Let’s make the proportion:
8 – 100%
x – 40% (multiply the cross by the cross)
x = 8 × 40/100 = 320/100 = 3.2 is the width of the rectangle.
P = 2 × (8 + 3.2) = 2 × 11.2 = 22.4 is our answer.