AB=10,
AP:PB=2:3,
∴AP=10÷(2+3)×2-4,
PB=6,
M为AP中点,AM=PM=1/2AP=2,
①若N为PB中点,PN=1/2PB=3,
∴MN=PM+PN=5cm,
②若N为AB中点,AN=1/2AB=5,
∴MN=AN-AM=3cm.
AB=10,
AP:PB=2:3,
∴AP=10÷(2+3)×2-4,
PB=6,
M为AP中点,AM=PM=1/2AP=2,
①若N为PB中点,PN=1/2PB=3,
∴MN=PM+PN=5cm,
②若N为AB中点,AN=1/2AB=5,
∴MN=AN-AM=3cm.