The average monthly salary of 12 workers and 3 managers in a factory was Rs. 600. When one of manager whose salary was Rs. 720, was replaced with a new manager, n average salary of team went down to 580. What is salary of new manager?

The total salary amount = 15 × 600 = 9000
The salary of the exiting manager = 720
Therefore, the salary of 12 workers and the remaining 2 managers,
= 9000 ? 720 = 8280
When a new manager joins, the new average salary drops to Rs. 580 for the total team of 15 of them
The total salary for the 15 people i.e., 12 workers, 2 old managers and 1 new manager =580 × 15 = 8700
Therefore, the salary of the new manager is,
9000 - 8700 = 300 less than that of the old manager who left the company, which is equal to 720 - 300 = 420

Alternatively,
The average salary dropped by Rs. 20 for 15 of them.
Therefore, the overall salary has dropped by 15 × 20=300
Therefore, the new manager's salary should be Rs. 300 less than that of the old manager,
= 720 - 300
= 420