Find the circumference of a circle whose diameter is 20 cm.

To solve this problem, remember that the length of a circle is equal to the product of its diameter by the number π. It was found that whatever the circle, the ratio of its length to diameter is a constant number. This number is usually denoted by the letter π. The number of π is approximately equal to 3.14. Let us denote the length of the circle by the letter P, and its diameter by the letter d and write down the formula. P = π * d, d = 20 cm.
P = 3.14 * 20 = 62.8 cm
Answer: 62.8 cm