Correct Answer - Option 3 : 85
Given:
The average of 10 friends is 85
The average of top 9 is 90
The average of bottom 9 is 80
Concept:
Total = average × total number of items
Calculations:
Total marks in maths = 85 × 10 = 850
Total marks of top 9 = 9 × 90 = 810
Marks of lowest marks getter = 850 – 810 = 40
Total marks of bottom 9 = 80 × 9 = 720
Marks of highest marks getter = 850 – 720 = 130
Average of highest and lowest marks getter = (130 + 40)/2
⇒ Average = 170/2
⇒ Average = 85
∴ The average of the highest and the lowest marks is 85
