60 students of Section A of Class XI, obtained 40 mean marks in Statistics, 40 students of Section B obtained 35 mean marks in Statistics. Find out mean marks in Statistics for Class XI as a whole.

Explanation

Given:
`N_(1)=60,barX_(1)=40,N_(2)=40,barX_(2)=35`
`"We know, "barX_(12)=(barX_(1)N_(1)+barX_(2)N_(2))/(N_(1)+N_(2))`
`:." "barX_(12)=(40xx60+35xx40)/(60+40)`
`:." "barX_(12)=(2,400+1,400)/100=(3,800)/100=38`
Thus, Combinaed Arithmetic Mean = 38.