How to Use Prime Factoring to Win Friends and Influence People

Alright, you might not win friends with this, but the more you can do arithmetic in your head… well… okay, you can’t influence people with it either. Regardless, it’s handy to know and helps with multiplication.

Yesterday I posted a couple of videos about factoring numbers into primes. Now it’s time to put those to work.

How about a rather simple one to get us started:

Here’s one that’s a little more challenging. The key is that you can combine the bits to something you’re more comfortable doing. I don’t like multiplying nines, so I avoid those.

Can you use this? Why or why not? Ha ha, just kidding – no essay questions here! – but if you do find a use for this, or if this annoys you, let me know in the comments.

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4 Responses to How to Use Prime Factoring to Win Friends and Influence People

  1. This is how I habitually multiply and divide, except I worked out how to do this in the fourth grade and call it “cancelling out” in my head, because we didn’t learn about prime numbers or factors until middle school.

    I remember doing it on a test for my IEP and utterly confusing the tester, who outright told me to stop and do it the stupid way – I mean “the way I was taught”. Which was stupid.

    • How wonderful, Uly, that you were able to hold on to your own method. We should encourage kids to develop arithmetic for themselves, as you did, instead of forcing down their throats “the stupid way.”

      Some kids will develop for themselves the way that is taught in the class, or they will want someone to show them so they can follow along. And they should be given the freedom to take what the teacher offers, or create their own method, as you did.

      Just because a child confuses a teacher or tester, does not give that grown-up the right to change the child’s methods.

      Thanks for sharing your story, Uly!

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