Chemistry
posted by Shelly .
At 20 degrees C ethanol has a density of 0.789 g/ml and H2O has a density of 1.0 g/ml. What is the % by volume of ethanol of a solution made by adding 50g of ethanol with 50g of H2O?

Use density = mass x volume to convert 50 g ethanol to volume and to convert 50.0 g H2O to volume.
%ethanol v/v = (volume ethanol/total volume)*100 = ? 
i thought that density = m/v?
i've done the math and i think you are right because based on the above formula my answer is 126.74%
However, i don't understand why if the density formula is as you stated?
1/50 = .02, 1/.789 = .01578
(0.01578/0.02) x 100 = 78.9%