(7) Daca o grinda de lemn are dimensiunile de 15 x 20 x 400cm, iar metrul cub (m) de lemn costa 1000 ron, cat costa
10 grinzi

Volumul grindei

15 cm = 0,15 m

20 cm = 0,2 m

400 cm = 4 m

V = 0,15 x 0,2 x 4 = 0,12 m³

10V = 10  x 0,12 m³ = 1,2 m³

1 m² ......... 1000 ron

1,2 m³ ..............x ron

x = 1,2x1000/1 = 1200 ron

V. Grindă:

15cm=0,15 m

20cm=0,2 m

400cm=4m

V=0,15•0,2•4=0,12³

10V=10•0,12m³=1,2m³

1 m².................1000 ron

1,2m³.............? ron

x=1,2•1000:1=1,200 adica 1200 ron

R=1200 ron