Question

there are three groups of student each contain 25,50and 25student respectively .The average mark that are obtained by the first two groups are 60and 50.the combined average of all the three groups is 58.what is average of the mark the mark that are scored by the third groups?
1)62
2)72
3)70
4)65
explain the answer ​

Answer 1

average mark of 3rd group = 72

Step-by-step explanation:

groups of student each contain 25,50and 25student respectively .The average mark that are obtained by the first two groups are 60and 50

let say average of 3rd group = x

total marks = 25×60 + 50×50 + 25×x

= 1500 + 2500 + 25x

= 4000 + 25x

total students = 25 + 50 + 25 = 100

combined average = 58

total marks = 58×100 = 5800

4000 + 25x = 5800

25x = 1800

x = 72

average mark of 3rd group = 72

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