Question

It costs $2.80 to make a sandwich at the local deli shop. To make a profit, the deli sells it at a price that is 170% of the cost. The sandwich sells for $ .

Answer 1

Namely, what is 170% of 2.80?   well, if we take 2.80 to be the 100%, what is the 170%?

$\bf \begin{array}{ccll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 2.80&100\\ x&170 \end{array}\implies \cfrac{2.80}{x}=\cfrac{100}{170}\implies \cfrac{2.80\cdot 170}{100}=x$