Of the 5 subjects, the average marks of Rakesh in first 3 subjects was 75 and the average marks in the last 3 subjects was 82. If his marks in the third subject was 66, then what was his average marks in all the 5 subjects?

Given:

The average mark of Rakesh in the first 3 subjects was 75

The average marks in the last 3 subjects were 82

Rakesh's marks in the third subject were 66

Formula:

Average = Total marks/Number of subjects

Calculation:

Find the total marks Rakesh scored in the first 3 subjects

Average = Total marks/Number of subjects 

Total marks in first three subject = 75 × 3 = 225

Find the total marks Rakesh scored in the last 3 subjects

Total marks in the last 3 subjects = 82 × 3 = 246

Find the total marks Rakesh scored in all 5 subjects

Total marks in all 5 subjects = Total marks in the first 3 subjects + Total marks in the last 3 subjects - Marks in the third subject

225 + 246 - 66

225 + 246 - 66

405

Find the average marks of Rakesh in all 5 subjects

Average marks in all 5 subjects = Total marks in all 5 subjects/Number of subjects

= 405/5

= 81

So, Rakesh's average mark in all 5 subjects was 81.