Question

Find a number such that 30% of it is 1260

Answer 1

well, that number is "x", which oddly enough is the 100%, now, we also know that 30% of that is 1260, so hmmmm

`\begin{array}{ccll} amount&\%\\ \cline{1-2} x & 100\\ 1260& 30 \end{array} \implies \cfrac{x}{1260}~~=~~\cfrac{100}{30} \\\\\\ \cfrac{ x }{ 1260 } ~~=~~ \cfrac{ 10 }{ 3 }\implies 3x=12600\implies x=\cfrac{12600}{3}\implies x=4200`