Question

I do not get the assignment

Answer 1

`\begin{array}{ccll} minutes&cost\\ \cline{1-2} 18 & 7.20\\ 43& c \end{array} \implies \cfrac{18}{43}~~=~~\cfrac{7.20}{c} \\\\\\ 18c=(7.20)(43)\implies c=\cfrac{(7.20)(43)}{18}\implies c=17.2`

well, another way to do it will be using the unit rate, unit rate of what?

well, we're concerned with 43 minutes and how much, so cost and minutes, so hmm we know 18 minutes is 7.20, how much is it for 1 minute only?

`\cfrac{\stackrel{ \$ }{7.20}}{\underset{ mins }{18}}\implies \cfrac{0.4}{1}\implies 0.4~(\$)/(mins)\qquad \textit{40 cents per minute} \\\\\\ \textit{how much for 43 minutes?}\qquad 43\cdot 0.4\implies 17.2`