4)
pt. perna albastră :
20+20+20=40+20=60 cm
sau:
20×3=60 cm
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pt. perna galbenă :
40+40+40=80+40=120 cm
sau:
40×3=120 cm
-------------------------------------
pt. perna mov
30+30+30=60+30=90 cm
sau:
30×3=90 cm
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rezolvarea inttr-un exercitiu :
(20×3)+(40×3)+(30×3)=60+120+90=180+90=270 cm de panglica necesara pentru toate trei pernele
