质数有; 11,17,19,37,41
合数有; 9,15,21,27,33,35,45,49,57,65,72,81
偶数有; 72
奇数有; 1,9,11,15,17,19,21,27,33,35,37,41,45,49,57,65,81
写出5个质数和5个合数
5个质数:2,3,5,7,11
5个合数:4,6,8,9,10,
1~30中质数有;2,3, 5 ,7 ,11 ,13 ,17 ,19 ,23 ,29.
1~30中合数有;4 ,6 ,8 ,9 ,10, 12, 14, 15 ,16 ,18 ,20, 21, 22 ,24 ,25 ,26, 27, 28 ,30 .
1~30中奇数有;1,3,5,7,9,11,13,15,17,19,21,23,25,27,29.
1~30中偶数有;2,4,6,8,10,12,14,16,18,20,22,24,26,28,30.
3的倍数有 3,6,9,12,15,18,21,24,27,30.
5的倍数有;5,10,15,20,25,30.
同时是2和3的倍数有6,12,18,24,30.
同时是3和5的倍数有15,30,
同时是2 3 5的倍数有30.