Solution: Draw a picture according to the meaning of the question. According to f being the midpoint of BC, BF=[ 1/5]AC= 1.5cm, the lengths of AC, BC and AB can be calculated. According to AE=[ 1/2]EB, the length of EB can be found, and then the answer can be found.

As shown in the figure,

∫BF =[ 1/5]AC = 1.5cm，

∴AC=5BF=5× 1.5=7.5cm，

F is the midpoint of BC,

∴BC=2BF=2× 1.5=3cm，

∴AB=7.5-3=4.5cm，

∫AE =[ 1/2]EB，

∴EB=[2/3]AB=[2/3]×4.5=3cm，

∴EF=EB+BF=3+ 1.5=4.5cm.

So the answer is: 4.5cm. ..

，3，AF=CF= 1.5，AC=7.5，AE=3.5，BE=7

EF=5.5，0，