123456789 + 987654321 = 1111111110
1 x 142857 = 142857 (same set of numbers)
2 x 142857 = 285714 (same set of numbers, different sequence)
3 x 142857 = 428571 (same set of numbers, different sequence)
4 x 142857 = 571428 (same set of numbers, different sequence)
5 x 142857 = 714285 (same set of numbers, different sequence)
6 x 142857 = 857142 (same set of numbers, different sequence)
7 x 142857 = 999999 (!!!)
multiply any number with 9 and the sum of the result = 9
1 x 9 = 9
2 x 9 = 18, 1 + 8 = 9
3 x 9 = 27, 2 + 7 = 9
4 x 9 = 36, 3 + 6 = 9
and so on,
a quick way to multiply:
22 x 9 = 198, 2 x 9 = 18, then insert 9 in the middle and you get 198
let's try the following:
33 x 9 = 297, 3 x 9 = 27, insert 9 in the middle
44 x 9 = 396
55 x 9 = 495
66 x 9 = 594
77 x 9 = 693
88 x 9 = 792
99 x 9 = 891
how about triplets? just insert 99 in the middle:
222 x 9 = 1998, 2 x 9 = 18, then insert 99 in the middle
333 x 9 = 2997
444 x 9 = 3996,
555 x 9 = 4995.
and so on ...
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