Find the circumference of a circle if its radius is 3.9.

In the problem statement, the radius of the circle is set and it is equal to R = 3.9 cm. To find the circumference, you need to know the value of the constant – the number n = 3.1 (as required by the problem statement).

We are looking for the length of a circle with a given radius.

We will search for the circumference using the following formula.

l = 2пR, where R is the radius of the circle, and we remembered the value of the number n above.

Substitute the known values into the formula and calculate the circumference:

l = 2 * 3.1 * 3.9 = 6.2 * 3.9 = 24.18 cm.

The length of a circle with a radius of R = 3.9 cm is 24.18 cm.

Answer: 24.18 cm.

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