Discussion of Question with ID = 099 under Percentages

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A number is first increased by 60%, and thereafter it is reduced by 60% again. What is the overall reduction?


36 %.


38 %.


34 %.


40 %.

Ans: a

Let us derive the shortcut formula first, so that you can remember it and use it when the need arises. Suppose the number is 100, and let the increase be x%. The number becomes 100 + x. When it is reduced by x%, we get 100 + x - $((100 + x) × x)/100$ = 100 + x - $(x + x^2/100)$ = 100 - $x^2/100$, hence a reduction of $x^2/100$ = 36%

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