A= (9+6)×2×3 = 90 m²- peretii clasei
tavanul 9×6=54
______________________
tota pereti=144 m²din asta scadem:
3×2,25×1,5=10,125 m² ferestre
1×2,3=2,3 m² usa
2×3=6 m² tabla
144-10,125-6-2,3=125,575 m²
daca un kg ajunge pt 8m²⇒125,575/8=15,69 cutii si cum nu poti lua jumatati de cutii inseamna ca ai nevoie de 16 cutii