Question

Os numeros x,y e 15 sao inversamente proporcionais aos numeros 30,20 e 8 . Determine x e y

Answer 1

$\frac{x}{ \frac{1}{20}} = \frac{y}{ \frac{1}{30}} = \frac{5}{ \frac{1}{8}}$

$\frac{x}{ \frac{1}{30}}= \frac{15}{ \frac{1}{8}}\\\\ x* \frac{1}{8}= 15* \frac{1}{30}\\\\ \frac{x}{8}= \frac{15}{30}\\\\ 30x=8*15\\\\ 30x=120\\\\ x= \frac{120}{30} = 4$

$\frac{y}{ \frac{1}{20}}= \frac{15}{ \frac{1}{8}}\\\\ y* \frac{1}{8}= 15* \frac{1}{20}\\\\ \frac{y}{8}= \frac{15}{20}\\\\ 20y=8*15\\\\ 20y=120\\\\ y= \frac{120}{20} = 6$

Veja que
 
6*20 = 120
4*30 = 120 
15*8 = 120