The magic number
There was a fascinating front-page article on September' 09 in a local English daily. It highlights the very interesting mathematical phenomena of the digit 9. Wednesday's date 09/09/09, if the added digit comes to:
0+9+0+9+0+9 = 27, adding these two digits 2+7 = 9!
Interestingly, for any multiples of 9, if the digits are added serially to the last single digit; it comes to 9. For example 9×358 = 3222 = 3+2+2+2=9. Take any number you choose and multiply it by nine, then add the digits to the last single digit the number that comes is 9!
This is a peculiar and interesting characteristic of the digit 9. I had forgotten all about it; but the article reminded me of it. Way back in
1946, when I was a student of class eight in Calcutta, our mathematics teacher showed this to us. It was a fascinating example for us and created a lot of interest, towards arithmetic in particular and mathematics in general-- a subject that many students avoid!
I wonder if mathematics teachers in Bangladesh schools demonstrate this peculiarity of the digit 9 to their students. I am sure it will create general interest in mathematics among school students. It will be interesting if any reader recalls their own school experiences with the digit 9! Will some mathematician among the readers kindly throw some light on this interesting phenomena of the digit 9?
However, I do not know anything about the lucky characteristics of the digit 9. In our younger days we used to consider the digit 7 a lucky number, not that I ever believed in it.
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