If the salary of a person is first increased by 15% and thereafter decreased by 12%, what is the net change in his salary?
1.2% increase
When a quantity changes successively by \(+a\%\) and then \(+b\%\), the net percentage change is \(a + b + \frac{ab}{100}\).
Here the first change is \(+15\%\) and the second is \(-12\%\), so \(a = 15\) and \(b = -12\).
Net change \(= 15 + (-12) + \frac{15 \times (-12)}{100} = 3 - \frac{180}{100} = 3 - 1.8 = 1.2\).
The result is positive, so the salary increases by \(1.2\%\).
Hence, the net change is a 1.2% increase.
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