The use of percentages seem fairly common but most students seem to be clueless when confronted with the percentage symbol %.
The symbol can be seen as the division sign tilted at an angle. Therefore division is involved. Also, the symbol consist of a 1 and 2 zeros. This tells us that we need to divide by 100. Thus, percentage simply means to divide by 100. For example, 20% is really 20 divided by 100 to give us 0.2