Riddle Me This: Halfway Glass

The most accurate way to determine whether the glass is half-full, more than half-full, or less than half-full is to tilt the glass sideways until the water touches the lip of the glass. Because the glass is a right cylinder, you can look at where the water towards the bottom of the glass is to determine how much water there is. If the water level at the bottom of the glass is above the corner, the glass is more than half-full. If it is below the corner, the glass is less than half-full.