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I'm studying a series on algorithms taught by "Abdul Bari" on youtube

Here is when he says "A into B" to talk about multiplying A by B

I know why some say "a times b" when talking about multiplication. I'm curious about the expression "a into b". Where might it come from?

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  • Here is a century-old attestation: books.google.com/… – user6726 Oct 9 at 17:01
  • It sounds all wrong to my ear, based on my experience with a variety of math instructors. Maybe it's a dialect thing. – aparente001 Oct 10 at 6:06
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This is an archaism that survives in Indian English. When I learned the times tables in the 70s, this is how I did it: "1 into 1 is 1", "1 into 2 is 2" etc. We also were taught '4 by 2 is 2', with 'by' standing for division.

You can see 17th and 18th century references to this usage, e.g., 'for two into two is Four' (Henry More, 1712); 'for two into three is six' (Margaret Cavendish, 1668)

Meanwhile, you can see a similar use in a non-Indian example here.

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    It seems that "by" has also changed meaning as well. Do you have any idea why the word "into" might be used? Because the word "times" arises naturally when asking "how many times do I add the same number" when speaking about multiplication. But I can't find such an analog for "into" – Francisco José Letterio Oct 10 at 11:56
  • The OED gives a meaning of 'into' as 'Used to indicate multiplication, as to multiply x into y (by considering the multiplicand replicated once for each unit of the multiplier).' Perhaps the verb 'multiply' got dropped over time? – user2474226 Oct 10 at 12:25
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    That's weird. If you asked me "What is 2 into 6" I would say "3". – DJClayworth Oct 10 at 13:28
  • @DJClayworth So would I, in fact I would tend to think of both "into" and "by" as referring to division as in "2 into 6 is 3" and "8 by 2 is 4". I don't think I would use either of them but that is what I would understand. – BoldBen Oct 18 at 12:58

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