线段AB=12厘米,点M是AB中点,点C在MB上且MC:CB=2:1,求线段AC的长?

问题描述:

线段AB=12厘米,点M是AB中点,点C在MB上且MC:CB=2:1,求线段AC的长?

10CM

AC=12*(1/2+1/2*2/(1+2))
=12(1/2+1/3)
=6+4
=10

AM=MB=AB/2=12/2=6,
MC=2/3MB=2/3*6=4,
AC=AM+MC=6+4=10.

MB=AB/2=12/2=6
MC/CB=2/1
MC=MB*(2/3)=6*(2/3)=4
AC=AM+MC
=AB/2+MC
=12/2+4
=10cm