AI generatedGeometry and measuresKS3 / GCSE

Radius or diameter from a circumference

Radius or diameter from a circumference.

  • Use C = 2πr or A = πr², as appropriate.
  • Undo multiplication first; undo the square with a positive square root when needed.

Example 1

A circle has circumference . Find its radius and diameter.

Circle geometry, not to scaleNot to scale
Substitute the circumference into C = 2πr.Double the radius to find the diameter.

Example 2

A circle has circumference . Find its radius and diameter.

Circle geometry, not to scaleNot to scale
Substitute the circumference into C = 2πr.Double the radius to find the diameter.

Your turn

Question 1

A circle has circumference . Find its radius and diameter.

Circle geometry, not to scaleNot to scale
Check answer
Substitute the circumference into C = 2πr.Double the radius to find the diameter.
Question 2

A circle has circumference . Find its radius and diameter.

Circle geometry, not to scaleNot to scale
Check answer
Substitute the circumference into C = 2πr.Double the radius to find the diameter.
Question 3

A circle has circumference . Find its radius and diameter.

Circle geometry, not to scaleNot to scale
Check answer
Substitute the circumference into C = 2πr.Double the radius to find the diameter.
Question 4

A circle has circumference . Find its radius and diameter.

Circle geometry, not to scaleNot to scale
Check answer
Substitute the circumference into C = 2πr.Double the radius to find the diameter.
Question 5

A circle has circumference . Find its radius and diameter.

Circle geometry, not to scaleNot to scale
Check answer
Substitute the circumference into C = 2πr.Double the radius to find the diameter.
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