Question

2 cocosi cantaresc tot atat cat 3 gaini. Opt cocosi si 9 gaini cantaresc 42 kg.cat cantaresc un cocos si o gaina stiind ca toti cantaresc la fel

Answer 1

notam c=cocosi; g=gaini
2c=3g
8c+9g=42kg

4×2c+9g=42
4×3g+3g=42
12g+3g=42
15g=42
g=42:15=>g=2,8kg
3g=2c
3×2,8=2c
8,4=2c
8,4:2=c=>4,2
Sper ca ai inteles! Succes!

Answer 2

Notam cat cantareste un cocos cu c 
Notam cat cantareste o gaina cu g
Informatiile din problema sunt:
2 x c = 3 x g
8 x c + 9 x g = 42
Inmultim prima relatie cu 4 si obtinem:
8 x c = 12 x g
Inlocuim 8 x c in cea de-a doua relatie cu 12 x g:
12 x g + 9 x g = 42
21 x g = 42
g = 42 : 21
g = 2 kg
Dar stim ca 2 x c = 3 x g, adica 2 x c = 3 x 2 = 6, deci c = 6 : 2, adica
c = 3 kg
Proba:
2 x 3 = 3 x 2, adica 6 = 6, adevarat
8 x 3 + 9 x 2 = 42, adica 24 + 18 = 42, adica 42 = 42, adevarat