Mathematics

Today I thought to write something light
But many among us will think maths is not light :)
And yet...

Mathematics is fabulous.
I think too many people nowadays use calculators even for the simplest of calculations.
There are so many peculiarities in the multiplication table alone

Whenever you have a square:

4x4 = 16

9x9 = 81

14x14 = 196

then the multiplication of its immediate neighboring numbers  is one less:

3x5 = 15              (16-1)

8x10 = 80            (81-1)

13x15 = 195         (196-1)

If you multiply numbers two units away from the square it is always 4 (2 to the power of 2) less:

2x6 = 12               (16-4)

7x11 = 77             (81-4)

12x16 = 192         (196-4)

If you multiply numbers three units away from the square, it is always 9 (3 to the power of 2) less:

1x7 =7                  (16-9)

6x12 =72             (81-9)

11x17 = 187         (196-9)

And this goes for all numbers, even the really big ones.
And it goes on for numbers further away from the square as well (e.g. 5 away, will be 25 (5 to the power of 2 less)

-1x9 = -9               (16-25)

4x14 =56               (81-25)

9x19 = 171          (196-25)

50x50 = 2500
49x51 = 2499 (1 less than 2500)
45x55 = 2475 (25 less than 2500)

Amazing? I think it is.
Does it matter? Perhaps not.
All of us will not stop checking our own calculus with our electronic calculators.
In the mean time, playing with numbers in your mind can be fun
And giving the solution to apparently complex calculus in a wink without access to electronics can impress bystanders quite a lot.  :)