Question

25 students average 84 on a test. another group of 20 students averages 66. find the overall average.

Answer 1

84*25=sum of all 25 students marks
66*20=sum of 20 students marks
total average=(84*25+66*20) / 25+20
             =(2100+1320)/45
            = 3420/45
            =76