Question

Tipping at the campus coffee cart, a medium coffee cost $\$1.65$. Mary Anne brings $\$2.00$ with her when she buys a cup of coffee and leaves the change as a tip. What percent tip does she leaves $?$

Answer 1

Find the percent tip given by Mary Anne:

Total amount of money possessed by Mary Anne is $\$2.00$.

Cost of a medium cup of coffee is $\$1.65$

Since the difference gives us the tip left by Mary Anne, it will be:

$$\begin{gathered} =2.00-1.65 \\ =0.35 \end{gathered}$$

So, the tip left by Mary Anne is $\$0.35$

Write the percent proportion:

$$\begin{gathered} \frac{a}{w}=\frac{p}{100} \\ \Rightarrow \frac{0.35}{2.00}=\frac{p}{100} \end{gathered}$$ (Substitute $0.35$ for $a$ and $2.00$ for $w$)

($p$ is the percent tip in the percent proportion)

Cross-multiply it to evaluate $p$:

$$\begin{gathered} 35=2p \\ \Rightarrow p=17.5\% \end{gathered}$$

Hence, Mary Anne leaves the percent tip of $\mathbf{17}\mathbf{.}\mathbf{5}\mathbf{\%}$.