Maths · Rung 16 of 30

Circles

The circumference is 2πr and the area of the circle is πr². The diameter is two radii. Here answers keep π (8π), which is exact; with π ≈ 3.14 you get the number.

Where this sits

This is where the ladder starts: nothing is needed before it.

Exercises from this rung

Generated by the app, from easiest to hardest

  1. How long is the circumference?

    • 12π
    • 24π
    • 6π
    • 36π

    Why Circumference = 2 × π × r = 2 × π × 6 = 12π (≈ 37.7).

    easier

  2. What is the area of the circle?

    • 36π
    • 72π
    • 12π
    • 6π

    Why Area = π × r² = π × 6² = 36π (≈ 113.1).

    in between

  3. The diameter is 6. How long is the radius?

    • 12
    • 4
    • 6
    • 3

    Why The radius is half the diameter: 6 ÷ 2 = 3.

    harder