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  • Writer's pictureJoanne Jacobs

Why kids need to know 3 x 9 = 27

The ninth-grader needed to multiple 3 x 9 to answer an algebra problem. She didn't have a calculator, and I wouldn't let her go look for one. After five minutes of guessing, she came up with 27. She failed algebra.


Credit: Karolina Grabowska/Pexels

Teaching students to be fluent in addition and multiplication is controversial, writes Stephen Sawchuk in Education Week. Some teachers think learning multiplication tables is boring, and "timed tests and 'mad minutes' of worksheet problem-solving" are stressful.


But cognitive scientists say "having these facts at their fingertips frees up working memory for students to attend to problem-solving, applying procedures to more difficult problems, and other tasks," he writes.


Students won't learn "deeper, conceptual math" if they're hung up on 3 x 9.

“Multiplication facts seem boring to us because we know them,” noted Dylan Kane, a 7th grade math teacher in the Lake County district in Leadville, Colo. “But successfully learning new things is motivating for students. Because it’s old and boring for us doesn’t mean it’s old and boring for them.”

In a survey for Education Week's excellent Math Foundations for All report, most math educators agreed that fluency in math facts is "essential" for students to be able to tackle higher-order, conceptual math problems, Sawchuk writes. "But more than a quarter said that it was 'helpful, but not essential'.”


For a long time now, educators have tried to skip past the fundamentals in both math and reading to get to the higher levels of learning. They don't want to "drill and kill" math facts or phonics. But trying to do math without automatic recall of math facts is a hard slog. You might call it the "flail and fail" method. For that matter, will kids who can't decode develop a love of reading?

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Guest
May 11, 2023

To understand the number 9 and multiplication...all you need to do is watch multiplication rock...


The big cat and that poor cute mouse gets beat up pretty good on the pool table, but it's a great

way to learn multiplication


2 x 9 = 18 (if you add the digits of the result you will always get the number 9, if you don't get the number 9, you've made a mistake somewhere) :)

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Guest
May 10, 2023

I have a kid who can't memorize for the life of him. So we did Beast Academy and now he can look at 9*3 and say "That's 30-3" and it works. If you understand numbers, then you can get by with just knowing 2s, 5s, and 10s.


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Guest
May 10, 2023
Replying to

I'm also not sure that all kids are capable of this degree of fluency? It basically requires "distribution property and seeing the shape of thinsg" on the fly. On the other hand, it's changed my life -- I grew up learning only the algorithms, and going through Beast Academy with my kids has FINALLY taught me accurate mental math!


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Guest
May 09, 2023

Any 9th grader who doesn't know 3*9 and can't figure it out with 5 minutes of guessing would never have learned it. And she definitely passed algebra the next time she took it, if she did her homework.

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Joanne Jacobs
Joanne Jacobs
May 10, 2023
Replying to

She retook algebra in summer school and passed.

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Guest
May 09, 2023

Take a look at people explaining the 'nines finger trick' on youtube. Compare that with the way Singapore Math delivers conceptual understanding and practice to automaticity. What takes longer to learn? What sticks with a student? The former is indeed facts at the fingertips, but does nothing to a. acquaint the child with the associative, commutative, or distributive laws that will need to be known by algebra instruction time or b. be useful for solving a word problem.


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Guest
May 09, 2023

So, when a kid sees "2x * 6x = 24" the first thing they should do is get out the calculator and multiple 2 times 6 to see what that comes to? Then, in a separate step, divide 24 by 12 to see how that comes out?


Who are the idiots who promote this nonsense and why are they never taken to task?

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