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 ?

81

Sum of marks in 1st 3 subjects = 75 x 3 = 225

Sum of marks in last 3 subjects = 82 x 3 = 246

Marks in 5 subjects = 225 + 246 - 66 = 405

Average marks in 5 subjects = 81