Question

Daca numerele a,b,c sunt direct proportionale cu numerele 3,5,7 iar suma lor este 105 aflati numerele

Answer 1

$a;b;c \ \ \ \ d.p. \\ 3;5;7 \\\\\\ \Longrightarrow \frac{a}{3}=\frac{b}{5}=\frac{c}{7}=k \\\\ a=3k \\ b=5k \\ c=7k \\\\ a+b+c=105 \\\\ 3k+5k+7k=105 \\\\ 15k=105 \ \ \ |:15 \\\\ \underline{k=7} \\\\\\ \boxed{a=3*7 \to 21} \\\boxed{ b=5*7 \to 35} \\ \boxed{c=7*7 \to 49}}$

Answer 2

a/3=b/5=c/7=k (k fiind o constanta care ne va ajuta sa aflam numerele)
Din egalitatile de mai sus ⇒ a=3k
                                        ⇒b=5k
                                        ⇒c=7k
Suma nr=105⇒a+b+c=105⇒3k+5k+7k=105⇒15k=105⇒k=105/15⇒k=7
a=3k⇒a=7*3=21
b=5k⇒b=35
c=7k⇒c=49