Verbum Hodiernum: VIGINTI

Today's word is VIGINTI, which is the Latin word for twenty.

The Roman numeral was written XX. You may think that is the letter X written twice, but this X is not a letter of the alphabet (it just looks like the letter "x") - instead, it is a symbol, an abstraction that represents the counting out of five (V) twice - one five below and one five above. And that V is not the letter V - instead, it is probably the schematic representation of a hand (five fingers). So, the two V symbols written together look like an X, but it's not alphabetical at all. It's mathematical.

Since I don't have any good proverbs or sayings to share with you about the number viginti, I thought I would report here a great finger counting game that I learned about in a grad school seminar; as I recall from that long-ago seminar, the report of this method was attributed to Bede, who said it was a Roman method - but I would love to have a real reference, so if anybody recognizes this old way of counting, please let me know!

How to multiply on your fingers:

This is a way to multiply numbers 5-9 on your fingers. Showing the numbers 1, 2, 3, or 4 with your fingers is easy; you just hold up that number of fingers. To be able to do this trick, you also need to know how to show the numbers 6, 7, 8 and 9 with ONE HAND ONLY, being able to show those numbers with either your left or your right hand. Here is how it goes:

LEFT		RIGHT
	To show the number 5, hold no fingers down, palm facing you, so all fingers are extended; here is how the number 5 looks when made with your left hand, and with your right hand:
	To show the number 6, hold one finger down, palm facing you; here is how the number 6 looks when made with your left hand, and with your right hand:
	To show the number 7, hold two fingers down, palm facing you; here is how the number 7 looks when made with your left hand, and with your right hand:
	To show the number 8, hold three fingers down, palm facing you; here is how the number 8 looks when made with your left hand, and with your right hand:
	To show the number 9, hold four fingers down, palm facing you; here is how the number 9 looks when made with your left hand, and with your right hand:

To multiply, do the numbers with both hands, and then COUNT the number of fingers down and multiply those by 10, and then MULTIPLY the number of fingers standing up, and then add the two numbers:

	6 multiplied by 7: 3 fingers down = 30 4 x 3 fingers up = 12 TOTAL 42
	9 multiplied by 9: 8 fingers down = 80 1 x 1 fingers up = 1 TOTAL 81
	7 multiplied by 8: 5 fingers down = 50 3 x 2 fingers up = 6 TOTAL 56
	8 multiplied by 5: 3 fingers down = 30 2 x 5 fingers up = 10 TOTAL 40

Try some more - it works!