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doua numere direct proportionale cu 2 si 5 , iar suma primului nr si 30% din al 2-lea nr e 14. Aflati numerele.


Răspuns :

[tex] \frac{a}{2} = \frac{b}{5} [/tex]
5a=2b ⇒ [tex]a= \frac{2b}{5} [/tex]
[tex]a+ \frac{30*b}{100} = 14[/tex]
[tex] \frac{2b}{5} + \frac{30b}{100} = 14 [/tex]
[tex] \frac{2b}{5} + \frac{3b}{10} = 14 [/tex]
[tex] \frac{2b*2}{10} + \frac{3b}{10} = 14 [/tex]
[tex] \frac{4b+3b}{10} = 14 [/tex]
[tex] \frac{7b}{10} = 14 [/tex]
[tex]7b=140 =\ \textgreater \ b= 20[/tex]
5a = 2b 
5a = 2*20
a = 8