Question

Tìm x, y, z biết 

x/y = 10/9 ; y/z = 3/4 và x - y + z = 78

Answer 1

Ta có : \(\frac{x}{y}=\frac{10}{9}\Rightarrow\frac{x}{10}=\frac{y}{9}\)

            \(\frac{y}{z}=\frac{3}{4}\Rightarrow\frac{y}{3}=\frac{z}{4}\Rightarrow\frac{y}{9}=\frac{z}{12}\)

Nên : \(\frac{x}{10}=\frac{y}{9}=\frac{z}{12}=\frac{x-y+z}{10-9+12}=\frac{78}{13}=6\) 

Do đó : \(\frac{x}{10}=6\Rightarrow x=60\)

             \(\frac{y}{9}=6\Rightarrow y=54\)

             \(\frac{z}{12}=6\Rightarrow z=72\)

Vậy x = 60 ; y = 54 ; z = 72