MathsYears 10–11Geometry - Properties of Shapes

Pythagoras in 3D

Apply Pythagoras' theorem in three-dimensional problems

What you'll learn

  1. 1

    Imagine you have a cardboard box — like a shoebox. The longest distance from one corner to the opposite corner, going through the middle, is the 3D diagonal.

  2. 2

    The 3D diagonal goes from one corner to the opposite corner. How many corners does a box have?

  3. 3

    Let's find the 3D diagonal of a box with sides: length 3 cm, width 4 cm, height 5 cm.

  4. 4

    A box has sides: length = 6 cm, width = 8 cm, height = 10 cm. Find the 3D diagonal.

  5. 5

    For a box with length = 5, width = 12, height = 13, what is the base diagonal?

  6. 6

    Now try this one: a box has length = 2, width = 2, height = 2. Find the 3D diagonal.

  7. 7

    What is the 3D diagonal of a cube with side length 5 cm? (Hint: base diagonal = √(5²+5²) = √50)

Practise Pythagoras in 3D with Whizlo

Free AI-tutored lessons, unlimited practice questions, and progress tracking for ages 14–16. Aligned to the UK National Curriculum.