6.

The diameter of a circle is 18 cm. What is its area in terms of π.

324π cm2

18π cm2

180π cm2

81π cm2

1 answer

To find the area of a circle in terms of π, you can use the formula:

\[ A = \pi r^2 \]

where \( A \) is the area and \( r \) is the radius of the circle.

Given the diameter of the circle is 18 cm, we can find the radius \( r \) by dividing the diameter by 2:

\[ r = \frac{18 \, \text{cm}}{2} = 9 \, \text{cm} \]

Now, substitute the radius back into the area formula:

\[ A = \pi (9 \, \text{cm})^2 \]
\[ A = \pi (81 \, \text{cm}^2) \]
\[ A = 81\pi \, \text{cm}^2 \]

Therefore, the area of the circle in terms of π is:

\[ 81\pi \, \text{cm}^2 \]

So, the correct answer is:

\[ 81\pi \, \text{cm}^2 \]