2023 AMC 8 第 9 题
先试着解答 2023 AMC 8 第 9 题，然后核对你的答案与视频与精心整理的解答，解答来自 LIVE by Po-Shen Loh。你也可以参加完整限时模拟考试、查看全部 2023 AMC 8 解答，或核对答案。
所有题目均经美国数学协会（MAA）官方合法授权使用。
9.
玛莱卡在山上滑雪。下图显示了她沿雪道滑行时，相对于山脚的海拔高度（米）。她总共有多少秒处在 米到 米之间的海拔高度？
Malaika is skiing on a mountain. The graph below shows her elevation, in meters, above the base of the mountain as she skis along a trail. In total, how many seconds does she spend at an elevation between and meters?
答案：B
小提示：
数出图像位于两个高度之间的时间区间
Count the time intervals where the graph is between the two heights
大提示：
图中可见的三个分段分别计算
Split the count into the three separate intervals visible on the graph
视频讲解：
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文字解答：
她第一次达到 米是在 秒时。
随后她在 秒后低于 米，这一段贡献 秒。
接着她在 秒时重新高于 米，并在 秒时再次达到 米。
这一段贡献 秒。最后她在 秒时低于 米。
再到 秒时她低于 米，最后一段贡献 秒。
三个时间段的总长度为 所以正确答案是 B。
The first time that she hits an elevation of meters is at seconds.
She then dips below meters after seconds. This adds seconds to the total answer.
Malaika then goes above meters at seconds. She hits meters again at seconds.
This adds more seconds to the total. She finally dips below meters for the last time at seconds.
She then falls below meters at seconds, finally adding seconds to the total time.
The desired total is Thus, B is the correct answer.
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