2005 AMC 8 第 11 题
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所有题目均经美国数学协会(MAA)官方合法授权使用。
11.
伯格维尔的销售税率为 。伯格维尔大衣店促销期间,一件原价为 的外套打 折扣。两名店员杰克和吉尔各自计算账单。杰克先按 加收 的销售税,再从总额中减去 。吉尔先从 中减去原价的 ,再对折后价加收 的销售税。杰克的总额减去吉尔的总额是多少?
The sales tax rate in Bergville is . During a sale at the Bergville Coat Closet, the price of a coat is discounted from its price. Two clerks, Jack and Jill, calculate the bill independently. Jack rings up and adds sales tax, then subtracts from this total. Jill rings up , subtracts of the price, then adds of the discounted price for sales tax. What is Jack’s total minus Jill’s total?
答案:C
小提示:
加税和打折都是乘法
Adding tax and taking the discount are both multiplications.
大提示:
乘法顺序不同结果相同
Multiplication gives the same result in either order.
解答:
杰克的总额是 美元。
吉尔的总额是 美元。
因为乘法满足交换律,这两个乘积相等,所以杰克的总额减去吉尔的总额为 。
所以正确答案是 C。
Jack’s total is dollars.
Jill’s total is dollars.
These products are equal because multiplication is commutative, so Jack’s total minus Jill’s total is .
Thus, C is the correct answer.
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