Question

Find the missing number:
it is not 10%, or 25%, or 5.5%

Answer 1

let's say the original number is "a".

`\bf \begin{array}ll \cline{1-1} \textit{a\% of b}\\ \cline{1-1} \\ \left( \cfrac{a}{100} \right)\cdot b \\\\ \cline{1-1} \end{array}~\hspace{5em}\stackrel{\textit{5\% of`

`\bf \stackrel{(105a)/(100)\textit{ increased by 5\%}}{\cfrac{105a}{100}+\cfrac{21a}{400}}\implies \cfrac{21a}{20}+\cfrac{21a}{400}\implies \cfrac{420a+21a}{400}\implies \cfrac{441a}{400} \\\\\\ 1.1025a\implies 1a+0.1025a\implies \stackrel{\textit{original}}{a} + \stackrel{\textit{10.25\% added}}{\cfrac{10.25}{100}a}`