5 dam-5 cm
30dm-3 cm
420cm
=> P=5+3+420=428cm
b) AB=4cm
BC=8cm
AC=6cm
=> P=4+8=6=18cm
c) AB=20cm
BC=5cm
AC=4,8cm
=> P=20+5+4,8=19,8 cm
d)AB=36dm
BC=7/9x36=28dm
AC=1/2x(36+28)=1/2x64=32 dm
P=36+28+32=96dm
ex3
AB+BC+AC=90dm
AB=2/3BC
AC=5/6AB=5/6X2/3BC=5/9BC
2/3BC+BC+5/9BC=90
BC(11/9+1)=90
BC(20/9)=90
BC=90:20/9
BC=81/2
