W/V and V/V is used to express concentration in % of the solution. V/V stands for Volume/Volume and is used when you mix 2 liquids together. when you mix equal volume of two solution together, you get a concentration of 50% V/V
Similarly, W/V stands for Weight/Volume and is used when a solid is dissolved in a liquid solution. 60% W/V would mean 600gm of solid is dissolved to make 1L of solution.
In case of hand sanitiser, the concentration of alcohol can be expressed by both volume or by weight. For e.g,
If we add 750ml of Ethyl Alcohol to 250ml of water, the resulting hand sanitiser solution would be 75% V/V.
Since the mass of Ethyl alcohol is less than of water, then to get the same concentration,
600g of Ethyl Alcohol is diluted in purified water to make up a total volume of 1000ml. Hence, the percent now becomes 60% W/V.
So the concentration of hand sanitiser 75% V/V equals 60% W/V.