2023 AMC 8 第 5 题

先试着解答 2023 AMC 8 第 5 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。

5.

一个湖中有 250250 条鳟鱼,还有其他多种鱼。一位海洋生物学家从湖中捕捉并放回 180180 条鱼作为样本,其中 3030 条被识别为鳟鱼。假设样本中鳟鱼占总鱼数的比例与湖中相同,湖中共有多少条鱼?
A lake contains 250250 trout, along with a variety of other fish. When a marine biologist catches and releases a sample of 180180 fish from the lake, 3030 are identified as trout. Assume that the ratio of trout to the total number of fish is the same in both the sample and the lake. How many fish are there in the lake?
12501250
15001500
17501750
18001800
20002000
答案:B
知识点:比与比例
小提示:
样本的 180180 条鱼中有 3030 条鳟鱼
The sample has 3030 trout out of 180180 fish
大提示:
鳟鱼占湖中所有鱼的 16\frac16
Trout are 16\frac16 of all fish in the lake
视频讲解:
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文字解答:
样本中鳟鱼比例为 30180=16\dfrac{30}{180} = \dfrac{1}{6}。因此湖中所有鱼数是鳟鱼数的 66 倍。
湖中鱼的总数为 6⋅250=15006 \cdot 250 = 1500。
所以正确答案是 B。
Note that 30180=16.\dfrac{30}{180} = \dfrac{1}{6}. This means that a sixth of the fish in the lake are trout, or in other words, the total number of fish is 66 times the number of trout.
Therefore, there are 6⋅250=15006 \cdot 250 = 1500 fish in the lake.
Thus, B is the correct answer.
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