The length of the rectangle is 12 cm and the width is one-fourth of its length. Find its perimeter and area.

In order to find the part of an integer value, you must divide it by the denominator of the fraction and multiply by its numerator.
Let us determine the width of the rectangle, provided that it is ¼ fraction of its length, equal to 12 cm:

12: 4 * 1 = 3 cm.

The area of the rectangle is calculated by the formula:
S = a * b = 12 * 3 = 36 cm².

Let’s calculate the perimeter:
P = 2a + 2b = 2 * 12 + 2 * 3 = 24 + 6 = 30 cm.