Question

Jerry earns money delivering packages for the neighborhood grocery store. In his first month his average tip

increased from $.25 to $.40. What was the percent of increase?

Answer 1

well, the percent increase is really 15 cents, because 0.40 - 0.25 = 0.15.

now, if we take 0.25 to be the 100%, what's 0.15 off of it in percentage?

`\begin{array}{ccll} amount&\%\\ \cline{1-2} 0.25 & 100\\ 0.15& x \end{array} \implies \cfrac{0.25}{0.15}~~=~~\cfrac{100}{x}\implies \cfrac{~~ ( 25)/(100 ) ~~}{(15)/(100)}=\cfrac{100}{x}\implies \cfrac{25}{100}\cdot \cfrac{100}{15}=\cfrac{100}{x} \\\\\\ \cfrac{5}{3}=\cfrac{100}{x}\implies 5x=300\implies x=\cfrac{300}{5}\implies x=60`