Question

m7 unit 1, lesson 6 comprehension check review

1. look at the circle below. it has a diameter of 20 cm.

diameter = 20 cm radius = 10 cm
a = πr²
a = π • r • r
a = 314 cm²
a) what is the approximate area of the circle (numerical)? use 3.14 for π.
b) what is the exact area of the circle (in terms of π)?

Explanation:

Step1: Find the radius

Given diameter $d = 20$ cm, and the formula $r=\frac{d}{2}$, so $r=\frac{20}{2}=10$ cm.

Step2: Calculate the approximate area

The formula for the area of a circle is $A = \pi r^{2}$. Using $\pi = 3.14$ and $r = 10$ cm, we have $A=3.14\times10^{2}=3.14\times100 = 314$ $cm^{2}$.

Step3: Calculate the exact area

Using the formula $A=\pi r^{2}$ with $r = 10$ cm, the exact - area is $A=\pi\times10^{2}=100\pi$ $cm^{2}$.

Answer:

A. 314 $cm^{2}$
B. $100\pi$ $cm^{2}$