Question

If 24% of a number is 90, find 8% of that number.

Answer 1

well, the value was actually "x", which oddly enough is the 100%, but we also know that 90 is 24% of that, so

`\begin{array}{ccll} Amount&\%\\ \cline{1-2} x & 100\\ 90& 24 \end{array} \implies \cfrac{x}{90}~~=~~\cfrac{100}{24} \\\\\\ \cfrac{x}{90} ~~=~~ \cfrac{25}{6}\implies 6x = 2250\implies x=\cfrac{2250}{6}\implies x=375`

now, let's find 8% of that

`\begin{array}c \cline{1-1} \textit{\textit{\LARGE a}\% of \textit{\LARGE b}}\\ \cline{1-1} \\ \left( \cfrac{\textit{\LARGE a}}{100} \right)\cdot \textit{\LARGE b} \\\\ \cline{1-1} \end{array}~\hspace{5em}\stackrel{\textit{8\% of 375}}{\left( \cfrac{8}{100} \right)375}\implies \text{\LARGE 30}`