September 8th, 2024

Why 4x8 and 6x8 are, surprisingly, some of the hardest times tables to remember

Certain multiplication facts like 4x8 and 6x8 are difficult for students due to associative interference. Educators can improve recall by spacing out related facts and gradually mixing them after initial learning.

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Why 4x8 and 6x8 are, surprisingly, some of the hardest times tables to remember

The article discusses why certain multiplication facts, specifically 4x8 and 6x8, are particularly challenging for students to remember. It highlights the concept of associative interference, where related knowledge can hinder recall. For example, when trying to remember 4x8, students may confuse it with similar facts like 4x6 or 3x8, leading to errors. Research indicates that a significant percentage of multiplication mistakes, potentially up to 90%, stem from this interference. The author suggests two pedagogical strategies to mitigate this issue: first, educators should avoid introducing related multiplication facts simultaneously to reduce cognitive load; second, once students have learned these facts in isolation, they should gradually mix them to help students differentiate between them. This approach mirrors weight training, where individuals start with manageable weights and progressively increase difficulty. By applying these strategies, educators can enhance students' ability to recall multiplication facts effectively.

- 4x8 and 6x8 are among the hardest multiplication facts for students.

- Associative interference can lead to confusion and errors in recalling multiplication facts.

- Over half of multiplication mistakes may be due to interference from related facts.

- Educators should space out the introduction of related multiplication facts to reduce cognitive load.

- Gradually mixing learned facts can help students distinguish between them and improve recall.

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By @saltcured - 5 months
Maybe I'm a bit abnormal or had some kind of mild defiance disorder as a student in the 80s. Despite testing high and being told I was "gifted", I never could memorize the multiplication table. I learned the diagonal (the squares) up to 11x11, but even as an adult am more likely to fast-forward through some sequential calculations in my mind rather than trust a memorized answer.

For something like 6x8 I'll still almost immediately decompose it into either 2x(3x8) or 6x8 = 8x8 - 2x8 = 64 - 16. And if I did the latter, I'd second guess myself as to whether I'm going to make fence-post errors in the subtraction.

Even something basic like 5x7 I might mentally turn into 5x5 + 5 + 5 and just mentally step through the answer 25..30..35 on a number line. I get more error prone when incrementing by 7.

As an aside, it kind of blew my mind when I discovered that my wife seems to work a completely different way "in floating point". She'll often come out with a good answer for the mantissa but having lost track of the exponent. My mental calculations don't work this way at all.

By @jasonjamerson - 5 months
I was forced (thankfully) to commit everything under 12x12 to just rote memory, is that not widespread?
By @Const-me - 5 months
For old-school software developers 4*8 is easy because both numbers are powers of 2. I compute expressions like that as 2 ^ ( log2(4) + log2(8) ) = 2^(2+3) = 2^5
By @fjfaase - 5 months
Took me the longest (about 40 years) to memorize 7x8. Before being able to memorize it, I would usually add 7 to 49. For some reason, the squares stuck in my mind rather easily. So, 7x7 and 8x8 are easier. I cannot remember having problems with 4x8 and 6x8. Maybe because 48 is double of 24, which is double of 12. I have to say that my performance IQ is much higher than my verbal IQ.
By @patrakov - 5 months
The conclusion is (or, rather, was) invalid for Soviet Russia. The reason is that a song for children by Eduard Khil specifically mentioned 6x8=48.

https://www.youtube.com/watch?v=WLMHWtregmw (at 1:38).

By @zug_zug - 5 months
This is fascinating. So it looks to me like the proposals is that our brain has a map from 6 -> "multiples of 6" and 8 -> "multiples of 8" and it triggers both nodes, and that our brain then finds the MOST stimulated node (i.e. numbers that are multiples of both 6 and 8).

Because 24 is a multiple fo 6 and 8 it's causing interference.

This seems believable, curious if there's hard data on this (that indeed 6x8 is the hardest and other numbers with shared multiples) but not curious enough to look it up.

By @hffffauasddw - 5 months
I typically never remember 6 x 8, so I rearrange it to make it easier to compute in my head, like so:

  6(8) 
  = 6(10 - 2) 
  = 60 - 12 
  = 60 - (10 + 2) 
  = 60 - 10 - 2 
  = 48
By @rossant - 5 months
My own mnemonics relies on arithmetic progressions for these two:

- 6x8 = 48 : 4-6-8

- 7x8 = 56 : 5-6-7-8

By @cozzyd - 5 months
in hex, they're among the easier ones to remember!