Answer:
68%
Step-by-step explanation:
the mean is calculated as
mean = [tex]\frac{sum}{count}[/tex]
calculate the sum for both classes
class 1
[tex]\frac{sum}{20}[/tex] = 64 ( multiply both sides by 20 )
sum = 1280
class 2
[tex]\frac{sum}{10}[/tex] = 76 ( multiply both sides by 10 )
sum = 760
combine the 2 sums and divide by count of both classes for overall mean
overall mean = [tex]\frac{1280+760}{30}[/tex] = [tex]\frac{2040}{30}[/tex] = 68%
