To calculate the area of the circle, we can use the formula for the area of a circle, which is:

$A = \pi r^2$

Where:

• $A$ is the area
• $r$ is the radius
• $\pi$ is approximately 3.1416

The radius $r$ is given as 21 mm. Now, let's calculate the area to 1 decimal place:

$A = 3.1416 \times (21^2)$

Let me compute that.The area of the circle is approximately $1385.4 \, \text{mm}^2$, rounded to 1 decimal place.

Would you like more details or have any questions?

Here are some related questions:

1. What is the formula for the circumference of a circle?
2. How would the area change if the radius doubled?
3. How do you convert the area from square millimeters to square centimeters?
4. What happens to the area if the radius is halved?
5. Can you calculate the diameter of the circle from the given radius?

Tip: Always make sure to use the correct units for your final answer, especially when converting between different unit systems.