# Vui với các con số

Nhân  37 với bội 3:
3 x 37 = 111
6 x 37 = 222
9 x 37 = 333
12 x 37 = 444
15 x 37 = 555
18 x 37 = 666
21 x 37 = 777
24 x 37 = 888
27 x 37 = 999
…………………………………………..
12345679×09=111111111

12345679×18=222222222

12345679×27=333333333

12345679×36=444444444

12345679×45=555555555

12345679×54=666666666

12345679×63=777777777

12345679×72=888888888

12345679×81=999999999

————————————–
Trapeze:

1 x 9 + 2 = 11
12 x 9 + 3 = 111
123 x 9 + 4 = 1111
1234 x 9 + 5 = 11111
12345 x 9 + 6 = 111111
123456 x 9 + 7 = 1111111
1234567 x 9 + 8 = 11111111
12345678 x 9 + 9 = 111111111
………………………………………………………..
Another Trapeze:
1 x 8 + 1 = 9
12 x 8 + 2 = 98
123 x 8 + 3 = 987
1234 x 8 + 4 = 9876
12345 x 8 + 5 = 98765
123456 x 8 + 6 = 987654
1234567 x 8 + 7 = 9876543
12345678 x 8 + 8 = 98765432
123456789 x 8 + 9 = 987654321
…………………………………………………………………..
And another one:

0 x 9 + 8 = 8
9 x 9 + 7 = 88
98 x 9 + 6 = 888
987 x 9 + 5 = 8888
9876 x 9 + 4 = 88888
98765 x 9 + 3 = 888888
987654 x 9 + 2 = 8888888
9876543 x 9 + 1 = 88888888
98765432 x 9 + 0 = 888888888
987654321 x 9 – 1 = 8888888888
9876543210 x 9 – 2 = 88888888888
…………………………………………………………….
987654321 x 09 = 08 888 888 889

987654321 x 18 = 17 777 777 778

987654321 x 27 = 26 666 666 667

987654321 x 36 = 35 555 555 556

987654321 x 45 = 44 444 444 445

987654321 x 54 = 53 333 333 334

987654321 x 63 = 62 222 222 223

987654321 x 72 = 71 111 111 112

987654321 x 81 = 80 000 000 001
………………………………………………………………

Nice one:
And finally, take a look at this symmetry:
1 x 1 = 1
11 x 11 = 121
111 x 111 = 12321
1111 x 1111 = 1234321
11111 x 11111 = 123454321
111111 x 111111 = 12345654321
1111111 x 1111111 = 1234567654321
11111111 x 11111111 = 123456787654321
111111111 x 111111111 = 12345678987654321
111.111.111 x 111.111.111 = 12.345.678.987.654.321