According to the meaning of the question, the sugar water is 80ml and the sugar content is 20%.

The volume of sugar in this cup of syrup can be calculated by multiplication.

The formula can be obtained, 80*20%= 16, that is, there is 16ml sugar in this cup of sugar water.

By subtraction, the water content can be obtained.

80- 16=64, that is, the water content is 64ml.

According to the meaning in the question, the sugar content becomes 10% after the sugar water is diluted.

The volume of diluted sugar water can be calculated by division.

The formula can be obtained,16/10% =160, that is, the volume of diluted sugar water is 160ml.

By subtraction, the amount of this glass of water can be obtained.

160-16 =144, that is, the volume of water is 144ml.

Then the amount of water added is 144-64=80,

So I added 80 ml of water.

Extended data:

This kind of problem belongs to the solution concentration problem in mathematics.

In production and life, we often encounter the problem of solution concentration. This kind of problem mainly studies the relationship among solvent (water or other liquid), solute, solution and concentration.

For example, water is a solvent, what is dissolved is called solute, and the mixture after dissolution is called solution. The percentage of solute in a solution is called concentration, also called percentage concentration.

Quantitative relationship:

Solution = solvent+solute

Concentration = Solute existing solution × 100%

Ideas and methods of solving problems: simple problems can be directly modified by formulas, and complex problems can be modified by formulas.

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