# 數學好好玩

數學好好玩

Nice one:
111,111,111  x  111,111,111 = 12,345,678,987,654,321

Trapeze:

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

0x 9 + 1 = 1

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

123456789 x 9+10 = 1111111111

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:

0x 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

12345679 x9=111111111

12345679 x18=222222222

12345679 x27=333333333

12345679 x36=444444444

12345679 x45=555555555

12345679 x54=666666666

12345679 x63=777777777

12345679 x72=888888888

12345679 x81=999999999