A parent established a college fund for his daughter. Each year the parent made a contribution to the fund, and each year he increased his contribution by a constant amount. If he made a contribution of $800 in the first year, by what amount did the parent increase his contribution to the fund each year? (1) The parent’s contribution to the fund in the 18th year was $7600. (2) The parent’s contribution to the fund in the 7th year was twice what it was in the 3rd year.
? Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient ? Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient ? BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. ? EACH statement ALONE is sufficient ? Statements (1) and (2) TOGETHER are NOT sufficient 答案是D。。。 可是我觉得是C
关键是“Each year the parent made a contribution to the fund, and each year he increased his contribution by a constant amount. ”这句怎么理解？ 我觉得说的意思是每年都会新增一个contribution，而且contribution本身每年都会增加固定数额 举个例子， 第一年的fund是1， 第二年contribution了1，fund变成2 第三年contribution本身增加了1，所以fund变成2+2=4 类推，之后变成4+3=7，7+4=11之类~
(1) The parent’s contribution to the fund in the 18th year was $7600. 意思就是 800+(800+I)+(800+2I)+...+(800+17I)=7600 可以求到I你这样理解，这个条件的意思就是“到第18年，fund变成了7600”，而不是“第18年的contribution是7600”
(2) The parent’s contribution to the fund in the 7th year was twice what it was in the 3rd year.
(1) The parent’s contribution to the fund in the 18th year was $7600. 意思就是 800+(800+I)+(800+2I)+...+(800+17I)=7600 可以求到I你这样理解，这个条件的意思就是“到第18年，fund变成了7600”，而不是“第18年的contribution是7600” 我理解的两者是一样的 反正只有一个人在往里面存钱 要不然你觉得contribution是什么呢？？ 但是照你的理解还是可以求得 800+17I=7600 更好求了
(2) The parent’s contribution to the fund in the 7th year was twice what it was in the 3rd year.
contribution是每年往里面投的钱啊，题干上都说了Each year the parent made a contribution to the fund但是这个contribution本身是会变的，因为each year he increased his contribution by a constant amount 也就是说，每年往fund里投的钱，都比前一年投的钱要多一个固定的数额。 比如 第一年有一个基数， 第二年往里面扔500， 第三年比第二年多扔100，就变成第三年扔600 第四年比第三年多扔100，所以第四年扔700......
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发表于 2011-7-14 17:50:26
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