Number 999

An interesting feature is the number 999 appears in the multiplication of it any other three-digit number. It turns out a six-digit product. The first three digits of it is a multiplied number minus one, and the remaining three numbers - "add-on" first to 9.

An interesting feature is the number 999 appears in the multiplication of it any other three-digit number

For example:

                                    572

573 x 999 = 572 427

                                    999

One has only to look at the next line in order to understand the origin of this feature:

                                                                  573 000

573 x 999 = 573 (1000 1) =         -573

                                                                  572 427

Knowing this feature, we can "instantly" multiply any three-digit number to the number 999:

947 x 999 = 946 053

509 x 999 = 508 491

              981 x 999 = 980 019 . .

And since the number 999 = 111 = 9 x 3 x 3 x 3 x 37, you can, again with lightning speed, write whole column six-digit numbers that are multiples of 37. Who is not familiar with the properties of the number 999, of course, do this unable. In short, you can arrange to uninitiated small sessions "instant" multiplication.

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