Question

if the radius of a circle is 10 cm, what is its circumference?

Explanation:

Step1: Recall the formula for the circumference of a circle

The formula for the circumference \( C \) of a circle is \( C = 2\pi r \) or \( C=\pi d \) (where \( d \) is the diameter and \( d = 2r \)). Here we use \( C = 2\pi r \), and we know that the radius \( r=10\space\text{cm} \).

Step2: Substitute the value of radius into the formula

Substitute \( r = 10\space\text{cm} \) into \( C=2\pi r \). So we get \( C = 2\times\pi\times10 \).

Step3: Calculate the result

Simplify \( 2\times\pi\times10 \), we have \( C = 20\pi\space\text{cm} \). If we take \( \pi\approx3.14 \), then \( C\approx20\times3.14 = 62.8\space\text{cm} \).

Answer:

The circumference of the circle is \( 20\pi\space\text{cm} \) (or approximately \( 62.8\space\text{cm} \)).