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From 2018 to 2019, Mohan’s annual salary increased by 10 percent and Arun’s annual salary decreased by 5 percent. If their annual salaries were equal in 2019, then Arun’s annual salary in 2018 was what percent greater than Mohan’s annual salary in 2018 ?

  • A.16·91
  • B.13·34
  • C.15·78
  • D.10·98

Answer: C

Arun's 2018 salary was about 15.78 percent greater than Mohan's.

Let Mohan's 2018 salary be M and Arun's A. In 2019 they were equal:

\[ \begin{aligned} 1.10\,M &= 0.95\,A \\ \frac{A}{M} &= \frac{1.10}{0.95} = \frac{22}{19} \\ &\approx 1.1579 \end{aligned} \]

So Arun earned about 15.79% more, which the paper prints, cut at two decimals, as 15·78.

Simply adding the two changes gives 15%, close but not offered. 10·98 is close to Mohan's 10% rise alone and ignores Arun's 5% fall; 16·91 and 13·34 do not fit the equation above.

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