If a number is increased from $80$ to $100$, the percentage increase is

If a number is increased from $80$ to $100$, the percentage increase is
  1. $20\%$
  2. $25\%$
  3. $30\%$
  4. $80\%$

Solution

Increase $= 100 - 80 = 20$. Percent increase $= \dfrac{20}{80} \times 100\% = 25\%$ (always taken on the original value).

Asked in: IMO

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