AMC8 2026

AMC8 2026 · Q5

AMC8 2026 · Q5. It mainly tests Rates (speed).

Casey went on a road trip that covered $100$ miles, stopping only for a lunch break along the way. The trip took $3$ hours in total and her average speed while driving was $40$ miles per hour. In minutes, how long was the lunch break?

Casey 进行了覆盖 $100$ 英里的公路旅行，途中只停下来吃了午餐。整个行程共花费 $3$ 小时，她驾车时的平均速度是每小时 $40$ 英里。问午餐休息了多少分钟？

(A) 15 15

(B) 30 30

(D) 45 45

(E) 60 60

Answer

Correct choice: (B)

正确答案：（B）

Solution

The average speed is $\frac{ \text{ Total distance } }{ \text{ Total time } }$, or $\frac{100}{3-t}$. Thus $\frac{100}{3-t} = 40 \Rightarrow 3-t = \frac{100}{40} \Rightarrow t = \frac{1}{2}$, which is $\boxed{ \textbf{(B) } 30}$ minutes.

平均速度是$\frac{ \text{总距离} }{ \text{总时间} }$，即$\frac{100}{3 - t}$。因此$\frac{100}{3 - t} = 40 \Rightarrow 3 - t = \frac{100}{40} \Rightarrow t = \frac{1}{2}$，即$\boxed{\textbf{(B) } 30}$分钟。

Topics

AR.007 Rates (speed)