A_______M_______B__N__C
AC=30
BC=2.8
deci AB=AC-BC=30-2.8=27.2
M mijloc ab, deci AM=MB=27.2:2=13.6
N mijoc BC, deci BN=NC=2.8:2=1.4
Deci MN=13.6+1.4=15 cm
La fel si celalalt caz
D_____G_____E___________H____________F
DE=5.4
EF=18
DG=GE=5.4:2=1.7
EH=HF=18:2=9
Deci GH=1.7+9=10.7 cm
DF=5.4+18=23.4