2020 AMC 12A 第 4 题
先试着解答 2020 AMC 12A 第 4 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 2020 AMC 12A 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。
4.
有多少个 位正整数，也就是从 到 （含端点）的整数，只含偶数数字且能被 整除？
How many -digit positive integers (that is, integers between and inclusive) having only even digits are divisible by
小提示：
能被 整除的数末位是 或 ，但末位还必须是偶数
A number divisible by ends in or but the last digit must also be even
大提示：
分别数每一位的选择数：首位不能是 。
Count the choices for each digit: the leading digit cannot be
解答：
要能被 整除，末位必须是 或 ，又因为所有数字都要是偶数，所以末位只能是 。
首位是非零偶数：，共有 种选择。中间两位各可以是任意偶数 ，各有 种选择。
总数为 。
因此，正确答案是 B。
To be divisible by the last digit is or and to be even it must be So the units digit is fixed.
The leading digit is a nonzero even digit: give choices. Each of the two middle digits is any even digit giving choices each.
The total is
Thus, B is the correct answer.
其他年份的第 4 题
- 1950 AMC 12
- 1951 AMC 12
- 1952 AMC 12
- 1953 AMC 12
- 1954 AMC 12
- 1955 AMC 12
- 1956 AMC 12
- 1957 AMC 12
- 1958 AMC 12
- 1959 AMC 12
- 1960 AMC 12
- 1961 AMC 12
- 1962 AMC 12
- 1963 AMC 12
- 1964 AMC 12
- 1965 AMC 12
- 1966 AMC 12
- 1967 AMC 12
- 1968 AMC 12
- 1969 AMC 12
- 1970 AMC 12
- 1971 AMC 12
- 1972 AMC 12
- 1973 AMC 12
- 1974 AMC 12
- 1975 AMC 12
- 1976 AMC 12
- 1977 AMC 12
- 1978 AMC 12
- 1979 AMC 12
- 1980 AMC 12
- 1981 AMC 12
- 1982 AMC 12
- 1983 AMC 12
- 1984 AMC 12
- 1985 AMC 12
- 1986 AMC 12
- 1987 AMC 12
- 1988 AMC 12
- 1989 AMC 12
- 1990 AMC 12
- 1991 AMC 12
- 1992 AMC 12
- 1993 AMC 12
- 1994 AMC 12
- 1995 AMC 12
- 1996 AMC 12
- 1997 AMC 12
- 1998 AMC 12
- 1999 AMC 12
- 2000 AMC 12
- 2001 AMC 12
- 2002 AMC 12A
- 2002 AMC 12B
- 2003 AMC 12A
- 2003 AMC 12B
- 2004 AMC 12A
- 2004 AMC 12B
- 2005 AMC 12A
- 2005 AMC 12B
- 2006 AMC 12A
- 2006 AMC 12B
- 2007 AMC 12A
- 2007 AMC 12B
- 2008 AMC 12A
- 2008 AMC 12B
- 2009 AMC 12A
- 2009 AMC 12B
- 2010 AMC 12A
- 2010 AMC 12B
- 2011 AMC 12A
- 2011 AMC 12B
- 2012 AMC 12A
- 2012 AMC 12B
- 2013 AMC 12A
- 2013 AMC 12B
- 2014 AMC 12A
- 2014 AMC 12B
- 2015 AMC 12A
- 2015 AMC 12B
- 2016 AMC 12A
- 2016 AMC 12B
- 2017 AMC 12A
- 2017 AMC 12B
- 2018 AMC 12A
- 2018 AMC 12B
- 2019 AMC 12A
- 2019 AMC 12B
- 2020 AMC 12B
- 2021 AMC 12A Spring
- 2021 AMC 12B Spring
- 2021 AMC 12A Fall
- 2021 AMC 12B Fall
- 2022 AMC 12A
- 2022 AMC 12B
- 2023 AMC 12A
- 2023 AMC 12B
- 2024 AMC 12A
- 2024 AMC 12B
- 2025 AMC 12A
- 2025 AMC 12B