The problem asks us to find the surface area $A$ of a sphere given its diameter $D = 19.8$ mm. We are also given that we should use $\pi = 3.14$ and round the final answer to the nearest tenth.

1. Problem Description

The problem asks us to find the surface area $A$ of a sphere given its diameter $D = 19.8$ mm. We are also given that we should use $\pi = 3.14$ and round the final answer to the nearest tenth.

2. Solution Steps

First, we need to find the radius $r$ of the sphere. The radius is half of the diameter:

$r = \frac{D}{2}$

$r = \frac{19.8}{2} = 9.9$ mm.

Next, we calculate the surface area $A$ of the sphere using the formula:

$A = 4 \pi r^2$

Substituting the given value of $\pi$ and the calculated value of $r$, we get:

$A = 4 \times 3.14 \times (9.9)^2$

$A = 4 \times 3.14 \times 98.01$

$A = 12.56 \times 98.01$

$A = 1230.9056$

Finally, round the result to the nearest tenth:

$A \approx 1230.9$

3. Final Answer

The surface area of the sphere is approximately $1230.9$ mm$^2$.