如图1，线段AC＝6cm，线段BC＝15cm，点M是AC的中点，在CB上取一点N，使得CN：NB＝1：2，求M...

问题详情：

如图1，线段AC＝6cm，线段BC＝15cm，点M是AC的中点，在CB上取一点N，使得CN：NB＝1：2，求MN的长．

【回答】

解：∵M是AC的中点，AC＝6，

∴MC＝AC＝6×＝3，·············································································· 1分

又因为CN∶NB＝1∶2，BC＝15，

∴CN＝15×＝5，·························································································· 3分

∴MN＝MC＋CN＝3＋5＝8，

∴MN的长为8 cm·························································································· 4分 

知识点：直*、*线、线段

题型：解答题