Question

Anna 在华盛顿特区一家餐馆用餐，餐费销售税为 $10\%$ 。她按税前餐费留下 $15\%$ 的小费，税也按小费前的餐费计算。她晚餐总共花了 $\$27.50$ 。她不含税和小费的餐费是多少美元？

Anna enjoys dinner at a restaurant in Washington, D.C., where the sales tax on meals is $10\%.$ She leaves a $15\%$ tip on the price of her meal before the sales tax is added, and the tax is calculated on the pre-tip amount. She spends a total of $\$27.50$ for dinner. What is the cost of her dinner without tax or tip?

$\$18$

$\$20$

$\$21$

$\$22$

$\$24$

答案：D

知识点：百分数一次方程

难度评级：900

解答：

设税前餐费为 $x$ 。税为 $0.1x$ ，小费为 $0.15x$ 。总花费满足所以 $x=22$ 。 $\begin{align*}x+0.1x+0.15x&=1.25x\\&=27.5\end{align*}$

所以正确答案是 D。

Suppose the original price is $x.$ Then, the tax is $0.1x$ and the tip is $0.15x.$ This makes the total payment equal to: $\begin{align*}x+0.1x+0.15x&=1.25x\\&=27.5\end{align*}$ Therefore, $x=22.$

Thus, the correct answer is D .

2012 AMC 10B 第 5 题

答案：D

难度评级：900

解答：

其他年份的第 5 题