After two successive increments, Gopal's salary became of his initial salary. If the percentage of salary increase in the second increment was twice of that in the first increment, then the percentage of salary increase in the first increment was
After two successive increments, Gopal's salary became of his initial salary. If the percentage of salary increase in the second increment was twice of that in the first increment, then the percentage of salary increase in the first increment was
Solution
Let the first increment
Then the second increment
The key insight here is that Gopal's salary became of his initial salary.
If his original salary was , then his salary increased by in total.
When we have successive percentage increases, we cannot simply add them together.
If your salary increases by first, then by next, the second increase is calculated on the already increased salary, not the original one. Hence, there is a compounding effect, and the total increase would be more than .
For two successive percentage changes and , the net percentage change is:
Net change
The third term accounts for the compound effect.
We substitute our values:
Net change
If we expand the equation, we will have to solve for the root. We can see there is and can reasonably use to test.
Therefore, the percentage of salary increase in the first increment was 25%.