The length of the rectangle is 7 mm. What is the perimeter of this rectangle if its area is 35 mm2?

First, we need to know the width of the specified shape. We recognize it using the equation, if we know that the area of this figure is equal to a * b (that is, the length times the width):
x * 7 = 35.
x = 35/7.
x = 5.
The width is 5 mm.
Knowing the length and width, we can find the perimeter of the shape. Keeping in mind that the perimeter is the sum of all the sides of the rectangle, we find it:
P = 5 mm + 5 mm + 7 mm + 7 mm = 10 mm + 14 mm = 24 m.
Second way to find the perimeter:
P = 5 mm * 2 + 7 mm * 2 = 10 mm + 14 mm = 24 mm.