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I know this because the only way you can write 65 as the product of two numbers is 1 65, 65 1, 5 13 or 13 5. You can find some other examples in my answer to an earlier question. It would be fun to actually do this, but I wouldn't use marbles since it is too easy for them to roll away. You could use pennies or m & m candies (or smarties if you are in Canada) or something where you have 85 identical things. Now form an array with some of them, not necessarily all of them but at least 60. The array can't have more than 9 rows and it can't have more than 9 columns. If you do this then let me know how many you used and how many rows and columns.  


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