1990 AMC 8 第 20 题
先试着解答 1990 AMC 8 第 20 题，然后核对你的答案与精心整理的解答，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 1990 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。
20.
个家庭的年收入从 到 不等。由于错误，最高收入在电脑中被输入为 。错误数据的平均数与实际数据的平均数相差多少？
The annual incomes of families range from to In error, the largest income was entered on the computer as The difference between the mean of the incorrect data and the mean of the actual data is
答案：A
小提示：
只有一个数据变了，所以只有总和改变；数据个数仍是 。
Only one value changed, so only the total sum changes; the count stays at
大提示：
先求这个错误输入让总和多了多少，再除以 。
Find how much the one wrong entry inflated the total, then divide that by
解答：
只有一个数据被改错。错误总和比实际总和多 。
这多出的金额分摊到 个家庭上，平均数相差 。
所以正确答案是 A。
Only one entry changed. The incorrect total exceeds the actual total by
Since this extra amount is spread over families, the means differ by
Thus, the correct answer is A .
其他年份的第 20 题
- 1985 AMC 8
- 1986 AMC 8
- 1987 AMC 8
- 1988 AMC 8
- 1989 AMC 8
- 1991 AMC 8
- 1992 AMC 8
- 1993 AMC 8
- 1994 AMC 8
- 1995 AMC 8
- 1996 AMC 8
- 1997 AMC 8
- 1998 AMC 8
- 1999 AMC 8
- 2000 AMC 8
- 2001 AMC 8
- 2002 AMC 8
- 2003 AMC 8
- 2004 AMC 8
- 2005 AMC 8
- 2006 AMC 8
- 2007 AMC 8
- 2008 AMC 8
- 2009 AMC 8
- 2010 AMC 8
- 2011 AMC 8
- 2012 AMC 8
- 2013 AMC 8
- 2014 AMC 8
- 2015 AMC 8
- 2016 AMC 8
- 2017 AMC 8
- 2018 AMC 8
- 2019 AMC 8
- 2020 AMC 8
- 2022 AMC 8
- 2023 AMC 8
- 2024 AMC 8
- 2025 AMC 8
- 2026 AMC 8