191–198 of 198 posts
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.
Why not?
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What is the advantage of using degrees (e.g. "30 degrees") versus radians (π/6)? Regardless, your observations seem to come down to "12 is highly composite and we use highly composite numbers for time"—valid, but interesting?
Radians are superior IMO. Using degrees for measurement is archaic compared to radians, but I imagine whole arabic-numeral numbers are more familiar than PI symbols in the learning process at the point in life when most kids are first learning geometry something related to angles. Understanding PI symbols for the first time could possibly come alongside an algebra curriculum, but I'm not a K-12 educator so if I had a…
And apparently, in what I have to assume is a related use:
> In surveying, the gradian is the default unit of angles in many parts of the world.
( https://en.wikipedia.org/wiki/Gradian )
If you ever fooled around with your calculator in school, you probably noticed that it provided angle measurement conversion between degrees, radians, and gradians; the idea has certainly not gone the way of the French Republican Calendar.
This type of post is perfect Hacker News material! 1) Challenge an existing assumption about something we all do 2) Hand-wave some first-order guesses as to why we do it 3) Get nerdy with code and graphs and come to your conclusion, along with helpful suggestions for bettering the reader With no prospect of the pre-decimal money system returning, I can only conclude that the logic behind this new priority is simply,…
But do we all learn tables up to 12? In the Netherlands it's only up to 10 for as far back as I know.
>Or, as Chris Carlson suggested to me, learn the near reciprocals of 100 (2 x 50 = 100, 3 x 33 = 99, 4 x 25 = 100, 5 x 20 = 100, 6 x 17 = 102, etc.), as they come up a lot. This is absolutely worthwhile, easy approximation of 1 or 100 divided by 6 or 8 in particular occurs regularly, and not enough people know it offhand. Hugely helpful. After 1-10, your energy is probably better spent on cool patterns and "tricks" w…
There is some use in knowing subsets of the time tables beyond 9: specifically M x N combinations For instance, if you know that 8x12 = 96, you know that 1/12 is approximately 0.08. And since 0.96/12 is exactly 0.08, you know that the remainder is 0.04/12 which gives you the .003333... in 0.0833333... Essentially, it supports numeric intuition. These higher times tables can be useful in long division. In long divisio…
You get this same intuition in a much better way by knowing that "since 1/8 is approximately 0.12, 1/12 is approximately 0.08".
Only in non-metric countries. Back in the British era of pounds, shillings, and pence, hardware had to be built to do arithmetic in that system. This resulted in one of the strangest, and most complex, purely mechanical computing devices ever built - the McClure Multiplying Punch [1], from Powers-Samas. This device came out in 1938. The comparable IBM machine was the IBM 602 Multiplying Punch, but IBM only did decima…
I disagree. 1. We have time. Days are 24 hours, a multiple of 12. 2. We still have time. Hours are 60 minutes, a multiple of 12. 3. Yet more time. Minutes are 60 seconds, a multiple of 12. 4. We have circles. There are 360 degrees in a circle, another multiple of 12. 5. The numbers 1, 2, 3, 4, 6 and 12 itself divide into 12 evenly. The next smallest number that has more factors than 12 is 24, which manages to be a mu…
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you forgot the one i use the most often - there are 12 months in a year. how many times do you calculate "X per year" in your head? i do it multiple times per day, and not just at work.
Probably should have included that. Meanwhile, reviewing my post it reminded me of my US History teacher in middle school telling me that the Conquistadors in the Americas were after the 5 Gs: Gold, Gold, Gold, God, and Glory. I listed five things: Time, Time, Time, Degrees and Factors. I'd be thrilled if someone could say the same thing but with all of the words starting with the same letter.
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In addition to the upward counting of time, memorizing the 12s column (I agree that the /human/ difficulty of learning 10s and 11s is mostly simple tricks to calculate those numbers on the fly) gives users the ability to work backwards and forwards with fractions of time based on 12s. Thanks to the seconds and minutes counting in 60s and hours and months (somewhat) counting in 12s knowing base 2, 3, 4, 6 and 12 is ex…
> Many baking items are also sold in units of 12 (E.G. eggs, 144 being that packet size that businesses buy in). We’ve solved that in Europe, too – they’re sold in packages of 10, and businesses buy in packages of 100.