1958 AMC 12 第 28 题
先试着解答 1958 AMC 12 第 28 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 1958 AMC 12 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。
28.
一个容量为 夸脱的散热器中装满了水。取出四夸脱并补入纯防冻液；再从混合液中取出四夸脱并补入纯防冻液。如此再进行第三次和第四次。最终混合液中水所占的比例为：
A -quart radiator is filled with water. Four quarts are removed and replaced with pure antifreeze liquid. Then four quarts of the mixture are removed and replaced with pure antifreeze. This is done a third and a fourth time. The fractional part of the final mixture that is water is:
小提示：
每次取出混合液，都会带走当前剩余水的相同比例
Each removal takes away the same fraction of whatever water remains
大提示：
每次更换后，原有水量的 留下
After one replacement, of the previous water remains
解答：
每次取出充分混合的散热器内容物的四分之一，因此留下当时水量的四分之三。四次更换后，水所占的比例为
所以正确答案为 B。
Each removal takes one-fourth of the well-mixed radiator contents, so it leaves three-fourths of the water then present. After four replacements, the water fraction is
Therefore, the correct answer is B.
其他年份的第 28 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
- 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