LCF 請列式加以說明

用戶20078

2008-12-06 1:56 am

1) 有粉筆一盒，數目在80枝以上，分給8個或12個學生都恰好分盡，問這盒粉筆最少有多少枝？

請列式加以說明

更新1:

2) 用15，10，18去除某數，餘數每次都是5，問這個數目最少是多少？

回答 (1)

The Little Prince of Mathematics

2008-12-06 3:02 am

✔ 最佳答案

1) We need to find a smallest C.F of 8 and 12, and it should be greater than 80.
8 = 2*2*2
12 = 2*2*3
Therefore, the L.C.F should be 24, and the common factor should be a multiple of 24 ( = 2*2*2*3)
Therefore, the minimum number of chalks is 96 ( = 24*4)

2) We need to find the L.C.F of 15, 10, 18 first, and add 5 to it and get the answer.
15 = 3 * 5
10 = 2 * 5
18 = 2 * 3 * 3
Therefore, the L.C.F is 2 * 3 * 3* 5 = 90. So, the answer is 90 5 = 95

2008-12-05 19:06:02 補充：
sorry, it should be L.C.M. (Lowest Common Multiple) instead of L.C.F (Lowest Common Factor).
The L.C.F. of all number should be 1. However, the value of L.C.M may varies.

參考: me

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