Summary


You need to remember that percentages are just proportions expressed out of one hundred. If you can remember this, you can work out that the equation you need for percentage calculations is:


Percentage = Proportion of Specific Item x 100 %

Percentage =     Amount of Specific Item     x 100 %
Total Amount of All Items

Finally, you need to understand what a percentage is because the concentration of chemicals can be expressed as a percentage.