Question

Becca visited 80 vendors at a job fair, and she took a pamphlet from 40% of them. How many pamphlets did Becca take?

Answer 1

how many were there? well, really there were "x", which oddly enough is the 100%, we also know that 40% of "x" is 80, so

`\begin{array}{ccll} amount&\%\\ \cline{1-2} x & 100\\ 80& 40 \end{array} \implies \cfrac{x}{80}~~=~~\cfrac{100}{40} \\\\\\ \cfrac{ x }{ 80 } ~~=~~ \cfrac{ 5 }{ 2 }\implies 2x=400\implies x=\cfrac{400}{2}\implies x=200`