[tex]\it 1m^2=100dm^2=10000cm^2\\ \\ 2,5kg=2,5\cdot1000g=2500g\\ \\ \mathcal{A}_{dreptunghi} =L\cdot\ell=25\cdot8=200cm^2[/tex]
Notăm masa dreptunghiului cu x.
[tex]\it 10000cm^2 - - - - - - - - 2500g\\ \\ 200cm^2 - - - - - - - - - - xg\\ \rule{160}{0.6}\\\\ \\ Avem\ propor\c{\it t}ionalitete\ direct\breve a \Rightarrow x=\dfrac{200\cdot2500}{10000}=\dfrac{50 0000}{10000}=5g[/tex]
