At first I thought it was the camera angle, but then I realized that the wires are actually bent, is that right, Bill? That is a beautiful little piece of engineering to keep those beads on the side you want them to be on.
As for the rows on the bottom... is it related to a calendar? weeks and days...? Thinking about 4 weeks per (lunar-ish) month... but still two rows of 10, but... that also equals 28 beads total on the bottom. Not sure!
You remind me that I never gave the answer to this question that I promised! My theory is that it is related to Russian currency of the time. The beads above the first line of four count rubles. There used to a quarter-ruble coin, much like the US quarter. So the first line of four counts quarter-rubles. Then there were kopeks, which were like US cents. There are 100 kopeks in a ruble. So the next two lines of 10 count kopeks. Then there were quarter-kopeks, like the old British farthing (a quarter of a penny). So the last line of four counts quarter-kopeks. I haven't verified this theory beyond the existence of those coins and the fact that the structure of the abacus fits with them.
Brilliant! Maybe you can do some special advising on a request we recently got from NYC Public schools to make an IM lesson that meets their NGMLS 1st grade standard NY-1 MD 3b: Recognize and identify coins (penny, nickel, dime, and quarter) and their value and use the cent
symbol (¢) appropriately.
and 3c: Count a mixed collection of dimes and pennies and determine the cent value (total not to exceed
pennies and dimes to me line up perfectly with 1st grade place value standards... nickels and quarters, that's a jump.
I am also now just realizing that this is actually another more elementary (pun-intended) version of the very first new custom lesson we wrote for NYC that was about unit conversions to meet one of their Algebra 1 standards.
I've never understood why it was the job of mathematics class to teach kids about coins. A lesson spent explaining what the coins look like is a lesson spent not teaching mathematics.
Talking about money in the context of unit conversions DOES make sense. And we have that right there in the CCSS in Grade 2 and Grade 4.
"Twenty nickels equals one dollar" or "five nickels equals one quarter" is the same concept as "twelve inches equals one foot" which is the same as the global understanding of fractions as nouns/numbers.
At first I thought it was the camera angle, but then I realized that the wires are actually bent, is that right, Bill? That is a beautiful little piece of engineering to keep those beads on the side you want them to be on.
As for the rows on the bottom... is it related to a calendar? weeks and days...? Thinking about 4 weeks per (lunar-ish) month... but still two rows of 10, but... that also equals 28 beads total on the bottom. Not sure!
And yes, the wires are curved. It's a beautiful thing.
You remind me that I never gave the answer to this question that I promised! My theory is that it is related to Russian currency of the time. The beads above the first line of four count rubles. There used to a quarter-ruble coin, much like the US quarter. So the first line of four counts quarter-rubles. Then there were kopeks, which were like US cents. There are 100 kopeks in a ruble. So the next two lines of 10 count kopeks. Then there were quarter-kopeks, like the old British farthing (a quarter of a penny). So the last line of four counts quarter-kopeks. I haven't verified this theory beyond the existence of those coins and the fact that the structure of the abacus fits with them.
Brilliant! Maybe you can do some special advising on a request we recently got from NYC Public schools to make an IM lesson that meets their NGMLS 1st grade standard NY-1 MD 3b: Recognize and identify coins (penny, nickel, dime, and quarter) and their value and use the cent
symbol (¢) appropriately.
and 3c: Count a mixed collection of dimes and pennies and determine the cent value (total not to exceed
100 cents).
:-)
Many thoughts on this...
pennies and dimes to me line up perfectly with 1st grade place value standards... nickels and quarters, that's a jump.
I am also now just realizing that this is actually another more elementary (pun-intended) version of the very first new custom lesson we wrote for NYC that was about unit conversions to meet one of their Algebra 1 standards.
It's all just language.
I've never understood why it was the job of mathematics class to teach kids about coins. A lesson spent explaining what the coins look like is a lesson spent not teaching mathematics.
Talking about money in the context of unit conversions DOES make sense. And we have that right there in the CCSS in Grade 2 and Grade 4.
"Twenty nickels equals one dollar" or "five nickels equals one quarter" is the same concept as "twelve inches equals one foot" which is the same as the global understanding of fractions as nouns/numbers.