# What will be the average mark of all the students if 80, 90, 70 are the average marks of the 3 groups of 4, 5, and 6 students respectively?

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What will be the average mark of all the students if 80, 90, 70 are the average marks of the 3 groups of 4, 5, and 6 students respectively?

1. 77.33
2. 79.33
3. 85
4. 75.33
5. None of these

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Correct Answer - Option 2 : 79.33

Given:

80 is the average marks of 4 students

90 is the average marks of 5 students

70 is the average marks of 6 students

Formula:

Average marks = total marks/ total number of students

Calculation:

If 80 is the average marks of 4 students then 80 × 4 = 320 is the total marks of 4 students.

If 90 is the average marks of 5 students then 90 × 5 = 450 is the total marks of 5 students.

If 70 is the average marks of 6 students then 70 × 6 = 420 is the total marks of 6 students.

Now the total number of students = (4 + 5 + 6) = 15

Required average = (320 + 450 + 420)/15

⇒ 1190/15 = 79.33

The average marks of all the students is 79.33