A person's salary is decreased by steps of 20\%, 15\% and 10\%. Approximately by what percent should the reduced salary be increased so as to get back the original salary?
(a)39\%
(b)44\%
(c)56\%
(d)63\%
Answer
Answer (as printed): D
Explanation
Let original salary $=₹ 100$. New salary = 90\% of 85\% of 80\% of ₹ 100 $$=₹\left(\frac{90}{100} \times \frac{85}{100} \times \frac{80}{100} \times 100\right)=₹ \frac{306}{5} .$$ Increase on $\frac{306}{5}=\left(100-\frac{306}{5}\right)=\frac{194}{5}$. $$\begin{aligned} \text { Increase on } 100 & =\left(\frac{194}{5} \times \frac{5}{306} \times 100\right) \%=\frac{9700}{153} \% \\ & =63.39 \% \approx 63 \% \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.