The closing price of Stock ~$X$~ changed on each trading day last month. The percent change in the closing price of Stock ~$X$~ from the first trading day last month to each of the other trading days last month was less than 50 percent. If the closing price on the second trading day last month was $10.00, which of the following CANNOT be the closing price on the last trading day last month?
$3.00
$9.00
$19.00
$24.00
$29.00
题意:上个月的股票价格每天都在变动。变动规律是:
第一天的closing price跟上个月任意一天的closing price的变动不超过50%
如果上个月第二天的closing price是$10,
问下面哪个选项不可能是上个月最后一天的closing price。
分析:因为题目给出第二天的closing price,
而且说第一天的closing price跟任何一天的closing price差别都不超过50%
(这里50%的变动,又有可能是增加50%或者减少50%)
所以我们可以求出第一天的closing price范围。
然后再根据第一天的closing price跟最后一天的price差别都不超过50%来求出最后一天的closing price范围。
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