This is a test of commonsense. Complete the next sentence:

How to use a cement mixer 
Pour approximately 1 gallon (3.79 l) of water into the concrete mixer. 
Be sure to use the correct amount of water per the cement mix instructions given by your specific mix label. If there is too much water added, the cement mix will come out too thin, become unmanageable, and not dry properly.
If there is not enough water, the mix will become too thick, it will not combine thoroughly, and will become unusable. Open the cement mix bag from the top and pour the entire contents into the cement mixer.