Question

7 in grinder on sale for $100.80 is marked as being 30% off. What was the original price

Answer 1

the original price was "x", which oddly enough is 100%.

so the sale price of the grinder was 100% - 30% = 70%, which we know is 100.80 bucks.

`\begin{array}{ccll} amount&\%\\ \cline{1-2} x & 100\\ 100.80& 70 \end{array} \implies \cfrac{x}{100.80}~~=~~\cfrac{100}{70} \\\\\\ \cfrac{ x }{ 100.80 } ~~=~~ \cfrac{ 10 }{ 7 }\implies 7x=1008\implies x=\cfrac{1008}{7}\implies x=144`