由题意,第二个数是5的倍数,其个位是5或0,那么第四数的个位是7或2 测试第四数:27,26不能被7整除;117,116 207,206 297,296 387,386 477,476,475,474,满足题意 72,71不能被7整除 162,161,160,159,满足题意 和最小为162+161+160+159=642 ...
1000以下的9的倍数有:9,18,27,36,45,54,63,72,81,90,99,108,117,126,135,144,153,162,171,180,189,198,207,216,225,234,243,252,261,270,279,288,297,306,315,324,333,342,351,360,369,378,387,396,405,414,423,432,441,450,459,468,477,486,495,504,513,522,531,540,549...
126,129,132,135,138,141,144,147,150,153,156,159,162,165,168,171,174,177,180,183,187,190,193,196,199就是除以3得到的商是整数,没有小数,没有余数,这样的数就是3的倍数。每位数的数字之和能被3整除就是3的倍数,比如说231这个数字,2+3+1=6,6÷2=3,所以231是3的倍数。