Pupils inestigate Kaprekar's routine.

This simple algorithm involving sorting and subtraction which always leads to 6174 when performed on four-digit numbers.

Teacher sheet is coming soon.

• Confidence in subtracting four-digit numbers.
• Familiarity with rule for divisibiity by 9.

• Distribute one copy of the sheet per pupil.
• Encourage pupils to work collaboratively.
• Optional - pupils to have access to a calculator.