Answer:
83.6
Step-by-step explanation:
total number of the class
= (12+18 )
=30 members
12 members had 80
18 members had 86
let the total marks had by the 12 members be x
also let the total marks had by the 18 members be y
80=[tex]\frac{x}{12}[/tex]
x=80×12
x=960
86=[tex]\frac{y}{18}[/tex]
y=86×18
y=1548
The average class mark
= [tex]\frac{x+y}{30}[/tex]
=[tex]\frac{1548+960}{30}[/tex]
=[tex]\frac{2508}{30}[/tex]
=[tex]\frac{418}{5}[/tex]
=83.6
the average class mark is 83.6
