Question

a cell phone battery uses 1/3 of its charge in 3/8 of a day. How much charge will it use in one day?​

Answer 1

$\bf \begin{array}{ccll}charge&day\\\cline{1-2}\frac{1}{3}&\frac{3}{8}\\\\x&1\end{array}\implies \cfrac{~~\frac{1}{3}~~}{x}=\cfrac{~~\frac{3}{8}~~}{1}\implies \cfrac{~~\frac{1}{3}~~}{\frac{x}{1}}=\cfrac{3}{8}\implies \cfrac{1}{3}\cdot \cfrac{1}{x}=\cfrac{3}{8}\\\\\\\cfrac{1}{3x}=\cfrac{3}{8}\implies 8=9x\implies \cfrac{8}{9}=x$