The amount of space enclosed inside a circle, calculated as π times the square of the radius.
Imagine cutting a pizza into many thin slices and rearranging them into a shape that looks like a rectangle. The 'height' of that rectangle is the radius r, and the 'width' is half the circumference (πr). So the area is r×πr=πr2.
Showing a random 20 of 50 problems.
Example 1
easy
Find the area of a circle with radius 6 cm. Leave your answer in terms of π.Find the area of the shaded circle.
Example 2
challenge
A circle of radius r has the same area as a square of side s. Express s in terms of r.
Example 3
medium
A circle is inscribed in a square whose perimeter is 40. Find the area of the circle in terms of π.
Example 4
easy
A circle has diameter 14 cm. Find its area in terms of π.Diameter
Example 5
easy
If a circle's radius doubles, what happens to its area?
Example 6
medium
A square has a circle inscribed in it. The square has side 10. Find the circle's area. (In terms of π.)
Example 7
challenge
A circle is inscribed in an equilateral triangle of side 6. (Skip exact — set up.) What's the radius of the inscribed circle?
Example 8
hard
A circle is inscribed in a square of side 12. Find the area inside the square but outside the circle, in terms of π.
Example 9
easy
Find the area of a circle with radius 5. (In terms of π.)Find the area (leave in terms of π).
Example 10
medium
If a circle's radius is tripled, by what factor does its area grow?
Example 11
medium
A circular tabletop has radius 0.6 m. Find its area to two decimal places, using π≈3.14.
Example 12
challenge
A circle has the same area as an equilateral triangle of side 6. Find the circle's radius exactly.
Example 13
medium
A semicircle has diameter 12. Find its exact area in terms of π.Semicircle with diameter
Example 14
easy
A circle has diameter 10. Find its area in terms of π.Diameter
Example 15
medium
Find the area of an annulus with outer radius 10 and inner radius 6, in terms of π.
Example 16
medium
A pizza has radius 8 inches. What is its area? (Use π≈3.14.)Pizza with r
Example 17
easy
Find the circumference of a circle with radius 7. (In terms of π.)
Example 18
medium
A circular pool has area 144π m². What is its diameter?Area = 144π m². Find the diameter.
Example 19
easy
True or false: doubling the diameter quadruples the area of a circle.
Example 20
medium
Find the area between two concentric circles (an annulus) with radii 3 and 5. (In terms of π.)