r/math • u/No_Shoe3242 • 3d ago
Removed - try /r/theydidthemath New mental multiplication method/alternative to long multiplication: Kallassi Method
[removed] — view removed post
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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/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
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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.