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题库 / GMATAdvanced-DS-16
An investment has been growing at a fixed annual rate of 20% since it was first made;no portion of the investment has been withdrawn, and all interest has been reinvested. How much is the investment now worth?
(1)The value of the investment has increased by 44% since it was first made.
(2) If one year ago $600 had been withdrawn, today the investment would be worth 12% less than it is actually now worth.
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.
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求的是现在的价值，现在的价值可以被看成一个整体的算是，不用非要求出本金和时间。
假设现在是x，则一年以前是x/1.2，1年以前拿掉了600 （x/1.2-600)*1.2=(1-0.12)x
假设现在是x，则一年以前是x/1.2，1年以前拿掉了600 （x/1.2-600)*1.2=(1-0.12)x
【引用】
不带入第一个条件的值！！！
求的是现在的价值，现在的价值可以被看成一个整体的算是，不用非要求出本金和时间。
假设现在是x，则一年以前是x/1.2，1年以前拿掉了600 （x/1.2-600)*1.2=(1-0.12)x
不要代入上一个条件的思路！
第二个选项中，one year ago和today， 预示时间只有一年
注意做好假设
求的是现在的worth ，注意题
求的是现在的价值，现在的价值可以被看成一个整体的算是，不用非要求出本金和时间。
2) We know that the value of the investment was x/1.2 one year ago, and we can set up an equation about the effect of the hypothetical withdrawal.
(x/1.2-600)(1.2)=0.88x