Question

如图,已知线段A、B（这儿有一个图）=24厘米,点C为AB上一点,CB=三分之二AB,点N为线段AC上一点,

Answer 1

因为CB = 2/3AB,AB = 24cm,

所以CB = 2/3*24 = 16cm,AC = AB -CB = 8cm;

又AN：NC=1：3,AN+NC=AC=8 cm;

所以NC=(3/(3+1))*AC = 6cm;

CM = 3MB,CM+MB = CB = 16cm,

既4MB=CB=16cm,所以 MB= 4cm,

CM = 3MB =12cm;

而NM = NC+CM=6+12 = 18cm;

所以MN长度为18cm