a4b5

來源: 於 2009-06-11 10:45:08 [舊帖] [給我悄悄話] 本文已被閱讀：次

不考慮a=0，這樣ab就不是兩位數了。
a0b can only be ab x 9 if such exist (a, b !=0 -> ab x 10 > a0b, ab x 8 ok:
100a + b = 9 x (10a + b)
10a = 8b
a:b = 4:5
the only digits satisfy this is a=4, b=5
405/45 =9, so 45 is the only solution.