The formula to find the circumference \( C \) of a circle is given by:
\[ C = 2 \pi r \]
where \( r \) is the radius of the circle. Given that the radius \( r \) is 21 cm and using \( \pi \) as \( \frac{22}{7} \), we can substitute these values into the formula:
\[ C = 2 \times \frac{22}{7} \times 21 \]
Now, let's calculate it step-by-step:
- Multiply \( 2 \) and \( 21 \):
\[ 2 \times 21 = 42 \]
- Now substitute that back into the circumference equation:
\[ C = \frac{22}{7} \times 42 \]
- To multiply \( \frac{22}{7} \) by \( 42 \), we can perform the multiplication:
\[ C = \frac{22 \times 42}{7} \]
Now calculate \( 22 \times 42 \):
\[ 22 \times 42 = 924 \]
- Now divide \( 924 \) by \( 7 \):
\[ C = \frac{924}{7} = 132 \]
Thus, the circumference of the circle is:
\[ \boxed{132 \text{ cm}} \]