Question

what is the area of a circle with a diameter of 10 milimeters? Estimate the area to the tenths place using 3.14 for pi.

a. 79 square mm
b. 15.7 square mm
c. 78.5 square mm
d. 314 square mm

Answer 1

To calculate the area of a circle, you can use the formula:

\[
\text{Area} = \pi r^2
\]

where \( r \) is the radius of the circle. The diameter of the circle is given as 10 millimeters, so the radius \( r \) is half of the diameter:

\[
r = \frac{10}{2} = 5 \text{ mm}
\]

Now we can plug the radius into the area formula. Using \( \pi \approx 3.14 \):

\[
\text{Area} = 3.14 \times (5)^2
\]
\[
\text{Area} = 3.14 \times 25
\]
\[
\text{Area} = 78.5 \text{ square mm}
\]

So, the area of the circle is approximately **78.5 square mm**.

The correct answer is: **c. 78.5 square mm**.