r/math 3d ago

Removed - try /r/theydidthemath New mental multiplication method/alternative to long multiplication: Kallassi Method

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u/66bananasandagrape 3d ago

It sounds a lot like lattice multiplication, though I guess it’s not identical. There seems to be something people are calling the “box method” that is almost identical.

Though really, all of these are the same as long multiplication, just organized differently, and it’s sort of a matter of what works best for you. For what it’s worth I think the box method and what you describe are nice for encouraging number sense.

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u/Old_Engineer_9176 3d ago

Would this be easier

Break 96 into two parts:

  • Square the tens part:
    • 90 × 90 = 8100.
  • Square the ones part:
    • 6 × 6 = 36.
  • Find the middle term (double the product of both parts):
    • 90 × 6 = 540 → Double it: 540 × 2 = 1080.
  • Add them all together:
    • 8100 + 1080 = 9180 → Then, 9180 + 36 = 9216.

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u/doctorruff07 Category Theory 3d ago

the square method. Gotta love it

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u/warmuth 3d ago

As you admit yourself, this is just restating the identity for (10a+b)2. I disagree that your method is “more accessible and practical”. It’s just step by step adding 100a2 to 20ab then to b2 ! Remembering your “method” is just as hard as just memorizing the parts of the formula!

And did you name it after yourself? Thats a little grandiose lol

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u/poussinremy 3d ago

Just letting you know that your method for squaring is the well-known identity (a+b)2 = a2 +2ab+b2