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Calculati lungimea unui dreptunghi care are latimea de 7 cm si perimetrul de 42 de cm.

Răspuns :

P=2×L+2×l 2L+7×2=42 2L+7=42:2 2L=21-7 2L=14 L=14:2 L=7
P=2L+2l
42=2L+2x7
42=2L+14
2L=42-14
2L=28
L=28:2
L=14cm