the monthly salary increased by Rs 4,620 over that two year period.
We know that first there is a 10% increase, such that after that, the monthly salary was Rs 23,100 per month.
In if the initial monthly salary was M, we must have:
M*(1 + 10%/100%) = M*(1.1) = Rs 23,100
M = Rs 23,100/1.1 = Rs 21,000
Now, to the Rs 23,100 there is another 20% increase, then the final monthly salary will be:
Rs 23,100*(1 + 20%/100%) = Rs 23,100*1.2 = Rs27,720
Then the difference between the final monthly salary and the initial is:
difference = Rs 27,720 - Rs 23,100 = Rs 4,620
This means that the monthly salary increased by Rs 4,620 over that two year period.
If you want to learn more about percentages:
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