Given: The average salary of the entire staff = Rs. 15000 The average salary of officers = Rs. 45000 The average salary of non-officers = Rs. 10000 Number of officers = 20 Calculations: Let the number of non-officers be x. Total member in entire staff = x + 20 Total salary of the entire staff = (x + 20) × 15000 ⇒ 15000x + 300000 ----(1) Total salary of officers = 20 × 45000 = 900000 Total salary of non-officers = x × 10000 = 10000x Total salary of the entire staff = 900000 + 10000x ----(2) From equation (1) and (2) ⇒ 10000x + 900000 = 15000x + 300000 ⇒ 5000x = 600000 ⇒ x = 120