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
上个月第一天和上个月其他任意交易日的收盘价变动都在50%以内,所以第一天和第二天比也在50%范围内,可能是增加50%也可能是降低50%,也就是第一天的收盘价范围在20/3(=10/1.5)至20(=10*1.5)之间。同样逻辑,第一天和最后一天的变动也在50%范围内,最后一天收盘价应该在10/3(=20/3*0.5)至30(=20*1.5)之间,所以A不对。
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