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Sending Cards

This challenge asks you to investigate the total number of cards that would be sent if four children send one to all three others. How many would be sent if there were five children? Six?

Dice and Spinner Numbers

If you had any number of ordinary dice, what are the possible ways of making their totals 6? What would the product of the dice be each time?

Method in Multiplying Madness?

Age 7 to 14
Challenge Level

If you are a teacher, click here for a version of the problem suitable for classroom use, together with supporting materials. Otherwise, read on...

If you had to work out $23 \times 21$ how would you do it?
What if you needed to work out $246 \times 34$?

Here are eight videos showing four different methods for working out the two multiplications. Can you make sense of them?

Grid Multiplication

$23 \times 21$

$246 \times 34$

Column Multiplication

$23 \times 21$

$246 \times 34$

Multiplying with Lines

$23 \times 21$

$246 \times 34$

Gelosia Multiplication

$23 \times 21$

$246 \times 34$

Once you have watched the videos, make up some multiplication calculations of your own and have a go at answering them using all four methods. Check that you get the same answer each time!

Here are some questions to consider:

Why does each method work?

What do the methods have in common?

What are the advantages and disadvantages to each method?

Extension challenge

Here is a video of another multiplication method, one where no writing down is needed along the way. Can you make sense of the video, and explain how this method works?