Imagine I have a bottle of 100ml which weight 90,135gr. I know that there is only water and alcohol in it. I know that the weight of water is 0,998 gr/cm3 and alcohol is 0,79 gr/cm3. And when I try to figure out how it is divided I'm doubting whether it is at all possible or it is by trying out around 42% alcohol. But is that true and how can you easily calculate this?
100 $cm^3 =90.135 g$
density is $0.90135 g / cm^3$
$0.90135 g / cm^3$ = $0.998x grams + 0.79y grams/ 100 cm^3$
redefine it as
$0.90135 g / cm^3 = (0.998x grams + 0.79(100-x) grams)/100$
$90.135=(0.998x grams + 0.79(100-x) grams)$
$90.135=0.998x grams + 79 - 0.79x grams$
$90.135=79 - 0.208x grams$
$53.5336538 mL$ of water.