Question

what is the area of a circle with a diameter of 10 millimeters? estimate the area to the tenths place using 3.14 for $pi$. (1 point)
15.7 square mm
79 square mm
314 square mm
78.5 square mm

Explanation:

Step1: Find the radius

The diameter \( d = 10 \) mm, and the radius \( r=\frac{d}{2}\). So \( r = \frac{10}{2}=5 \) mm.

Step2: Use the area formula for a circle

The area of a circle is \( A=\pi r^{2} \). We use \( \pi = 3.14 \) and \( r = 5 \) mm. So \( A=3.14\times5^{2} \).

Step3: Calculate the area

First, \( 5^{2}=25 \). Then \( 3.14\times25 = 78.5 \) square mm.

Answer:

78.5 square mm (corresponding to the option with 78.5 square mm)