How many water molecules are needed to break down an oligosaccharide that contains 10 glucose units

An Oligosaccharide is any carbohydrate of from three to six units of simple sugars (monosaccharides). A large number of oligosaccharides have been prepared by partially breaking down more complex carbohydrates (polysaccharides). Most of the few naturally occurring oligosaccharides are found in plants.

It takes 10 units of water molecules to break down an oligosaccharide that contains 10 glucose units. 
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Gay-lussac's law i think.