标题: GWD3-4 [打印本页] 作者: Eileenl 时间: 2010-11-1 22:38 标题: GWD3-4 In the year following an eight-cent increase in the federal tax on a pack of cigarettes, sales of cigarettes fell ten percent. In contrast, in the year prior to the tax increase, sales had fallen one percent. The volume of cigarette sales is therefore strongly related to the after-tax price of a pack of cigarettes.
The argument above requires which of following assumptions?
A. During the year following the tax increase, the pretax price of a pack of cigarettes did not increase by as much as it had during the year prior to the tax increase. B. The one percent fall in cigarette sales in the year prior to tax increase was due to a smaller tax increase. C. The pretax price of a pack of cigarettes gradually decreased throughout the year before and the year after the tax increase. D. For the year following the tax increase, the pretax price of a pack of cigarettes was not eight or more cents lower than it had been the previous year. E. As the after-tax price of a pack of cigarettes rises, the pretax price also rises 选了B，为何选D啊？作者: Eileenl 时间: 2010-11-1 22:46
顶~作者: Eileenl 时间: 2010-11-2 08:18
再顶~作者: eshopaholic 时间: 2010-11-2 22:10
after-tax price = pre-tax price + tax
tax涨了，并不等于after-tax price涨。若pre-tax price跌了，可能after-tax price没变，就不能说销售量的下降和after-tax price有关作者: Eileenl 时间: 2010-11-2 22:54
" For the year following the tax increase, the pretax price of a pack of cigarettes was not eight or more cents lower than it had been the previous year"又怎么证明了sales 和tax 有关呢？作者: 熊熊加小怪 时间: 2010-11-3 18:09
D选项不是用来证明sales 和tax有关的 只是一个assumption 原文推理sales和tax有关时中间少了一环链接，就是3楼说的那个公式作者: Eileenl 时间: 2010-11-4 21:57