Åk 6–9

3.1 Calculating Percentage
 It’s sports day in school.  The class which has the largest proportion students attending will get a prize. Foto: Fredrik Enander

 In class 9A, there are 25 students. Of these were 19 present. So 19 of 25 students were at sports day. In class 9B, there are 20 students Of these 15 were present. So 15 of 20 students were at sports day.

How can you decide which class had the larger proportion of student attending?

One way to compare is to use percent.
We calculate how many students would have been present if the classes had had an equal amount of students: 100 students. Then we use what we have already learned multiplying the fraction. Now it is easier to compare.

In 9A, 76 % of the students were present and in 9A, 75 % of the students were present. 9A had the largest proportion of students at sports day and wins the prize.  You can in a simple way calculate the percent, if you know the part and the whole. Example:
In Sweden, as of the 31st of December 2006, there live 1,407 people who were 100 years old or older.  Of these 219 were men.  How many percent were men?

Part:  219 (number of men)
Whole: 1,407 (total number of people)

 Percentage (of men) = 219 ≈ 0.16 = 16 % 1,407