The total distance around the outside of a circle; equal to π times the diameter or 2πr.
Imagine wrapping a string tightly around a circular jar lid, then straightening the string out. That length is the circumference. No matter the size of the circle, the circumference is always π times the diameter—roughly 3.14 laps of the diameter around the edge.
Showing a random 20 of 50 problems.
Example 1
medium
A clock's minute hand is 7 cm long. How far does its tip travel in one hour? Use π≈22/7.
Example 2
medium
The perimeter of a semicircular region (arc plus diameter) of radius 10 is what, in terms of π?Semicircular region with radius 10; perimeter = arc + diameter.
Example 3
hard
A circular running track has circumference 400 m. A runner completes 5 laps. Find the distance.
Example 4
medium
A wire of length 66 cm is bent into a circle. Find its radius using π≈22/7.
Example 5
medium
Two circles have radii in ratio 2:5. What is the ratio of their circumferences?
Example 6
hard
A circle is inscribed in a square of side 14. Find the difference between the square's perimeter and the circle's circumference. Use π≈22/7.
Example 7
easy
A circle has circumference 30π. Find its radius.Circumference = 30π; find radius r.
Example 8
medium
If a circle's radius is tripled, what happens to the circumference?
Example 9
challenge
A wheel rolls one full revolution without slipping. The center moves how far in terms of the radius r?
Example 10
challenge
A circular sector has arc length 8π and central angle 240∘. Find the radius.240° sector with arc length 8π; find radius r.
Example 11
medium
Find the arc length of a 120∘ sector in a circle of radius 9 in terms of π.120° sector of circle with radius 9; find the arc length.
Example 12
hard
Find the arc length corresponding to a central angle of 1 radian in a circle of radius 5.
Example 13
easy
A bicycle wheel has radius 0.35 m. How far does it travel in one full rotation? (Use π≈3.14.)
Example 14
hard
Two pulleys of radius 5 are 20 apart. Find the belt length using π≈3.14.
Example 15
easy
A circle has diameter 14. Find its circumference using π≈22/7.Circle with diameter 14; use π ≈ 22/7.
Example 16
hard
A regular hexagon has perimeter 48. Find the circumference of its circumscribed circle in terms of π.
Example 17
easy
If you double a circle's radius, what happens to its circumference?
Example 18
easy
A circle has radius 7. Find its circumference in terms of π.Circle with radius 7; find circumference.
Example 19
easy
What ratio does π represent?
Example 20
easy
Find the circumference of a circle with diameter 14 cm. Leave your answer in terms of π.Circle with diameter 14 cm; use C = πd.