1.8 Which per cent is it?
You probably agree that comparing percentages can be easier than comparing fractions. When we have a certain quantity, how do we write it as a percent of another, usually larger, number?
For example, if 42 people out of a group of 70 people agree to participate in a new community project, what percentage of the group is this?
Whenever you have a part of a group and the whole of the entire group, you can calculate the percentage by first expressing this as a fraction. So the number in the whole group tells you the denominator and the number in the part group the numerator for the fraction. You can then turn this fraction successfully into a percentage.
So in this case, the fraction is 
. To turn this into a percentage, first multiply by 100 per cent and then simplify:
(Note: you also could have simplified 
to 
first and then turned it into a percentage.)
These calculations show us that 60 per cent of the group agree to participate in the community project.
As you know, the calculation 
can be performed even quicker with a calculator, as can the other percent calculations.
To recap:
To express one number as a percentage of another:
- Write the numbers as a fraction and convert the result into a percent by multiplying by 100 per cent.