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Is there any point to the 12 times table?

blog.wolfram.com

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Re: Is there any point to the 12 times table?

#91

Post by lmm »

lukeschlather wrote: post #76
jameshart wrote: post #61

Earlier quoted context omitted.

But that's not really an argument for learning your twelve times table. In fact it's an argument that basically it's trivial to learn your twelves if you already know your threes and fours - the twelves are the numbers that appear in both lists. Or you can just skipcount your four times table. Overall, seems to argue against having to learn it.

Maybe. But the thing is if it's easier to memorize the composites, why not skip primes entirely over 5? Just memorize 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 . I'd have to run the numbers. It would be interesting to consider different subsets. I also think adding in 15 would probably worth the extra number for real-world datasets.

> Maybe. But the thing is if it's easier to memorize the composites, why not skip primes entirely over 5? Just memorize 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 .

Isn't that backwards? 7 is the hardest, so you spend more time on it, not less.

Re: Is there any point to the 12 times table?

#92

Post by cromulent »

JackFr wrote: post #38
zanny wrote: post #10

Earlier quoted context omitted.

That is only yet another reason in literally infinite ones why the US needs to actually push metric units. We bleed our stupidity into the UK and Canada while the rest of the world makes sense.

> another reason in literally infinite ones There are perhaps about three good reasons to push metric units, and the vast majority of us don't find them compelling enough to care. It's truly a non-issue.

As soon as I read your comment I thought about the Mars Climate Orbiter.

https://en.wikipedia.org/wiki/Mars_Climate_Orbiter

Re: Is there any point to the 12 times table?

#93

Post by kstrauser »

sandworm101 wrote: post #32
btilly wrote: post #19

Earlier quoted context omitted.

Makes sense..until you talk about time. Time makes no sense.

If you want to terrify an american, ask them about switching to metric time. https://en.wikipedia.org/wiki/Metric_time This comes up all the time for me as americans use a different date format. I've had contract negotiations grind to a halt because someone was doing math based on 06/05/15 rather than 05/06/15.

I write everything either ISO or spelled out. Your dates would be 2015-06-05 or "June 6, 2015". It's an easy quick that everyone seems to be comfortable with.

Re: Is there any point to the 12 times table?

#94

Post by mark-r »

sandworm101 wrote: post #32
btilly wrote: post #19

Earlier quoted context omitted.

Makes sense..until you talk about time. Time makes no sense.

If you want to terrify an american, ask them about switching to metric time. https://en.wikipedia.org/wiki/Metric_time This comes up all the time for me as americans use a different date format. I've had contract negotiations grind to a halt because someone was doing math based on 06/05/15 rather than 05/06/15.

Switch to ISO format. There's less confusion in 2015-05-06. Although the one time I tried to push for it, at a company with plants in both the US and Ireland, I couldn't quite get agreement and we settled on 2015-MAY-06.

Re: Is there any point to the 12 times table?

#95

Post by rglovejoy »

martin-adams wrote: post #51
zeveb wrote: post #11

Twelve has more divisors than ten (1, 2, 3, 4, 6 & 12 vs 1, 2, 5 & 10). If we were really smart, we'd switch from base 10 to base 12: many more 'decimals' (really duodecimals) would be non-repeating. One can very quickly count by twelves on the joints of one's fingers, using the thumb as an index (0-143 is a much larger range than 0-10, and it's easier to hold one's hands in the shape necessary). If we were really sm…

>> If we were really smart, we'd switch from base 10 to base 12 But I only have 10 fingers! On a practical note, wouldn't that mean inventing 2 new symbols to represent 10 and 11 as single digits, otherwise I could see that getting very confusing. You could't really use A and B, as then some people would be unable to find the correct seat on an airplane.

There was an episode of "Schoolhouse Rock" that was about just this ("Little Twelvetoes"). After the number nine, they suggested two new numbers, "dek" and "ell", and for "10", call it "doe".

Re: Is there any point to the 12 times table?

#96

Post by lmm »

lordnacho wrote: post #39
SixSigma wrote: post #3

I recently worked with a person who had to do her three times table using her hands, starting from 3. She would still struggle at about 6 or 7 times. We worked behind the counter in a builder's merchant. She is no longer working for us.

I had a job once where we hired a derivatives trader who couldn't multiply 8 and 4. In the job interview. At my next job we hired another trader who came up to me and said "what does the little 2 in a superscript mean?". As in what does 3^2 mean? Both very friendly people.

If you're paying a human trader it's for their friendliness, not their ability to do arithmetic. The computers can do the calculating.

Re: Is there any point to the 12 times table?

#97

Post by waxjar »

geofft wrote: post #25

Even in metric countries, there are still 24 hours in a day, so being able to have a sense of what 36 hours is or what 96 hours is is useful.

I don't think this comes up that often.

It's easier to speak in terms of days and halves of days. Often this is accurate enough.

Re: Is there any point to the 12 times table?

#98

Post by weinzierl »

lordnacho wrote: post #57

There's lots of questions thrown up by this. If people need to know times tables, do they also need to know powers of 2? They come up quite often if you deal with computers. What about squares? Anyone doing polynomials later on will be using them constantly. My sense is you will end up memorising the things that come up anyway, so why be so strict? You'll end up teaching kids that math is a memory game. So for fun, w…

   9,81 m/(s*s)
   3E8 m/s 
   6.022E23 
   1.602E-19 As
   9.109E-31 kg
   1.381E-23 J/K
   1/137 (Rarely needed it, it’s just so easy to remember)
   8h*19d*12m is ca. 1800 h/y
   65 is ASCII A
I know the numbers in my sleep but always have to think twice about the units. Somehow I never can remember the gravitational constant and the Planck constant.

Re: Is there any point to the 12 times table?

#99

Post by [deleted] »

pc86 wrote: post #24
BillTheCat wrote: post #17

Earlier quoted context omitted.

A simple trick: For 11 x a 2-digit number you can simply take the first digit of the 2-digit number then the 2 digits of the number added together then the last digit of the 2-digit number. Ex: 11 * 12 = 132 or 1, 1+2, 2. 11 * 45 = 495 or 4, 4+5, 5. For numbers which sum to more than 10 add the carry to the first number ex: 11 * 59 = 649 or 5, 5+9 = 14 so add 1 to the initial 5 and keep the 4, 9.

I'm 29 and never heard this before. Neat!

[deleted]

Re: Is there any point to the 12 times table?

#100

Post by threatofrain »

dnautics wrote: post #29
btilly wrote: post #28

Earlier quoted context omitted.

Easy divisibility is the reason why when we switched to metric, the one thing that didn't switch is time. Which means that, for example, converting from m/s to km/h is a mess. (You have to multiply by 3.6, can you easily do that in your head?) With a base 12 version of everything you would have 1/12 of a day being 2 hours, 1/144 of a day is 10 minutes, and 1/1728 of a day is 50 seconds. These units would give us both…

decimals cause huge problems for computers. How do you represent 0.6 as a floating point? In the long run, the correct solution is for everything to be binary.

Perhaps I'm wrong, but I believe that nothing can stop the problem that some quantities cannot be finitely represented, but I don't see why rationals are a problem because computers can finitely represent them with no information loss if they treat these numbers symbolically. We only have 0.1 + 0.2 != 0.3 issues due to using an imprecise but fast number representation system.
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