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How do I fill in this table

I'm confused on how to answer this question. Which I will attach at the bottom.... does it want me to dilute the hydrogen peroxide concentration to 80 60 40 20 percent using different amount of water but 40cm3 of hydrogen peroxide consistent ? And how would i do this as I'm bad at maths

The solution must always equate to 40cm cubed at whatever concentration you use. so for 80 percent you would basically divide 40 by 100 and times by 80 (since 80 percent is the same as 80/100). this gives you 32. Which is the volume of hydrogen peroxide you will have at 80% concentration. Then you must fill the remaining cm cubed with water to make it equal 40cm cubed.