First draw a table like the one above. Then in each of the squares put whatever number you want.

Add the top row (A+B) Then the bottom row (C+D) then the sum of both

(A+B) + (C+D).

Then go down so A+C and B+D then the sum of *those *two. (A+C)+(B+D). Notice anything?

That is not all! Now do the diagonals! A+D and B+C. Add the sums. Yep, the same number!!

This was in Alex’s math book today and we tried several different combinations and every time we ended up with each of the sums matching!

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This entry was posted on October 28, 2009 at 9:26 pm and is filed under homeschooling. You can follow any responses to this entry through the RSS 2.0 feed.
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October 31, 2009 at 6:46 am

This trick will work with any amount of squares. The idea is that the same numbers will always total the same no matter what order they are placed in. I don’t know if you are working on division yet, but a cool trick is that if you want to find out if a numer is evenly divisable by 3, then see if the sum of the digits is evenly divisable by three. 91 is not 93 is (10vs12)

Dad

November 1, 2009 at 10:26 pm

I will remember that trick! He has done some division but not a whole lot. Thanks!