100squareChoose a colour. Put a line through 4,6,8,10 … on the 100 square grid. Carry on until you get to 100 crossing out the rest of the two times table. You do not cross through the first number in the table but it may already be crossed out.

Change colour. Put a line through 6,9,12,15 … Do the rest of the three times table. What do you notice? Talk to a partner.

Now do the same with the other tables up to 9.

What do you notice?

What patterns do you see?

Which numbers are coloured twice? Or 3 times? Why?

Would you get the same result if you stopped after colouring the 7 times table and did not do the eight and nine times table.? Why?

See Teacher Notes Patterns of Multiples Seive.

This activity is named after a Greek called Eratosthenes who invented it.

You can find an interactive class version of Eratosthenes’ Sieve here and more about this activity on NRICH.

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7 Responses to Grades 6 to 9 Patterns of Multiples – Seive the Primes

  1. Avatar Margaret says:

    Doing Maths on computer on is amazing!I really appreciate the oppertunity Aimssec granted me to broaden my horizon.The next step will be to look for a donation for computers to impart this new knowledge to the learners and also making it possible for them to experience transformation in our school environment.

  2. Avatar Llaka Esther says:

    This activity is thought provoking.

  3. Avatar Rankotsane Violet says:

    I think doing mathematics on a computer will a whole lot of fun. Learners will enjoy it.

  4. Avatar Nana Martina says:

    Ive just started with it. I hope I find it as much useful as you.

  5. Avatar Bukeka Tembakazi says:

    I found the activity quiet challenging but i enjoyed going through it.

  6. Avatar Dorothy Dolly says:

    working with numbers is very interesting . it needs more concentration to learners to get the correct answer.

  7. Avatar Rankotsane Violet says:

    Aimssec is a breakthrough to bring change in our underprivileged schools .Aimssec rocks.

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