Why 24?

Write down three consecutive whole numbers none of which is a multiple of three. If you can’t do it, explain why.

Multiply any two consecutive even numbers together. Why is the product always a multiple of eight?

Take any prime number greater than 3, square it, subtract one and divide by 24.

Make a statement about what you notice about squaring prime numbers, subtracting 1, and dividing by 24 (a conjecture) and prove that what you say is always true.

Click here to download the WHY 24 worksheet.

See the Notes for Teachers.

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This activity is adapted from the NRICH task Why 24 with permission of the University of Cambridge. All rights reserved.