Va rog frumos ex. 3 si ex.4 ' sunt clasa 9
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3)P=2l+2L
l=2/3*L
P=2*2/3L+2l
P=4/3L+2L
30=4/3L+6/3L
30=10/3L
90=10L
L=9cm
l=2/3*9=6cm