Salary in USD = Current LKR salary / USD rate for pegging
Pegged salary = Salary in USD * Current USD rate
Example - If salary is 210,000 LKR & pegging rate is 210
Current Salary in USD = 210,000 / 210 = 1000 USD
Pegged Salary in March (if USD = 270) = 1000 USD * 270 = 270,000 LKR
Pegged Salary in April (if USD = 300) = 1000 USD * 300 = 300,000 LKR