Question

如图，C、D是线段AB上的两点，点C是AD的中点，AB=10cm,AC=4cm，求DB的长度

Answer 1

AC=AB/(1+2+3)=AB/6
MC=AB/12
CD=2AB/(1+2+3)=AB/3
DB=3AB/(1+2+3)=AB/2
DN=2DB/(2+3)=2DB/5=AB/5
MN=MC+CD+DN=AB/12+AB/3+AB/5=AB*37/60=18.5CM

Answer 2

AC是4的话，C又是AD的中点，那CD也是4吧，AD不就求出来了吗。再用AB-AD，DB=2