
Testing Percentage
 
Let's see how you got on!
In a maths class of 30 pupils, 40% are girls. 1 out of 3 pupils also studies physics. Half the boys have a mobile phone, whilst 6 girls have them. Three of the girls have a boyfriend at the moment.
 What percentage of the class are boys?
Total percentage is always 100%
Percentage of boys = 100%  40% = 60%
 How many boys are there in the class?
60% of 30 is 0·6 × 30 = 18
 What number of pupils also study physics?
1/3 of 30 = 10
 What percentage of the class have a mobile phone?
Boys: 0·5 × 18 = 9
Girls: 6
Total = 6 + 9 = 15.
Percentage = 15 ÷ 30 = 0·5 = 50%
 What percentage of girls don't have a boyfriend?
Number of girls without = 12  3 = 9
Fraction of girls = 9/12 = 0·75
Percentage of girls without a boyfriend = 75%

Did you get 100%  if so, well done  if not, do you know where you went wrong?
