Answer:
86%
Step-by-step explanation:
The mean is calculated as
mean = [tex]\frac{sum}{count}[/tex]
The sum for the class is calculated as
[tex]\frac{sum}{30}[/tex] = 70 ( multiply both sides by 30 )
sum = 2100
The sum of the 20 boys is
[tex]\frac{sum}{20}[/tex] = 62 ( multiply both sides by 20 )
sum = 1240
The sum for the 10 girls is therefore 2100 - 1240 = 860
Thus the mean mark for the girls is
mean = [tex]\frac{860}{10}[/tex] = 86%
