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Circle Area Quiz

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Questions and Answers

What is the formula for the area of a circle?

πr^2 (correct)

πd

r^2

2πr

If the radius of a circle is doubled, how does the area change?

It remains the same.

It increases by a factor of eight.

It doubles.

It quadruples. (correct)

Which of the following describes how to calculate the area of a circle with a diameter of 10 units?

Use the formula $5^2$. (correct)

Use the formula $2.5^2$.

Use the formula $10^2$.

Use the formula $r^2$ where $r$ is 10.

What value of π would you use if you want to estimate the area of a circle as approximately 3.14?

<p>π = 3.14</p> Signup and view all the answers

What happens to the area of a circle if its radius is reduced by half?

<p>Area is reduced to one-quarter.</p> Signup and view all the answers

Study Notes

Area of a Circle

The formula for the area of a circle is A = πr², where A is the area and r is the radius.
Doubling the radius increases the area by a factor of four. If r is doubled to 2r, then A becomes π(2r)² = 4πr².

Calculating Area with Diameter

To calculate the area of a circle with a diameter of 10 units, first find the radius which is 5 units (diameter / 2).
Use the area formula: A = π(5)² = 25π square units.

Estimating with π

For an estimation of the area of a circle as approximately 3.14, use π ≈ 3.14. This approximation simplifies calculations.

Effect of Reducing Radius

Reducing the radius by half results in the area being reduced to one-fourth its original size. If r is halved to 0.5r, then A becomes π(0.5r)² = 0.25πr².

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Description

Test your knowledge on the area of a circle with this quiz! You will explore formulas, changes in area with radius adjustments, and methods for calculation. Perfect for students learning geometry concepts about circles.