Correct Answer - Option 1 : 1020
Given
The average salary of all the Staff in a bank = Rs. 600
The average salary of all 12 officers = Rs. 4000
The average salary of the rest Staff = Rs. 560
Formula Used
Average = Sum of observation/No. of observation
Calculation
Let the number of rest of the staff in the Bank = x
Total salary of rest of staff members in the bank = Rs. 560x
Total salary of 12 officers = 12 × 4000 = Rs. 48000
Total salary of all the staff of the bank = 600 (12 + x)
⇒ 48000 + 560x = 600 (12 + x)
⇒ 48000 + 560x = 7200 + 600x
⇒ 600x - 560x = 40800
⇒ 40x = 40800
⇒ x = 1020
∴ The number of rest of the staff in the Bank is 1020
