救救我啊数学一道急急

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lightgarden

楼主

发表于 2011-9-24 12:08:45 | 显示全部楼层

IMO:
two digits are same, and the remaining is different:
Group1 : 711,722,733..766,788,799 (8 in total)
Group2: 800,811,822,833...877,899(9 in total)
Group3: 900, 911,922,933...988 (9 in total)
Group4: 707, 717, 727,737...767,787,797 (9 in total)
Group5: 808,818,828...878,898 (9 in total)
Group6: 909,919,929...989 (9 in total)
Group7: 770,771...(9 in total)
Group8: 880,881...(9 in total)
Group9: 990,991...(9 in total)

Total: 80