1987 AMC 8 第 15 题

先试着解答 1987 AMC 8 第 15 题,然后核对你的答案与精心整理的解答,解答来自 LIVE by Po-Shen Loh。你也可以参加完整限时模拟考试、查看全部 1987 AMC 8 解答,或核对答案。

所有题目均经美国数学协会(MAA)官方合法授权使用。

15.

一个促销广告写着:“按原价买三条轮胎,第四条轮胎只要 $3\$3。”山姆在促销中花 $240\$240 买了一套四条轮胎。一条轮胎的原价是多少?
A sale ad read: “Buy three tires at the regular price and get the fourth tire for $3.\$3.” Sam paid $240\$240 for a set of four tires at the sale. What was the regular price of one tire?
$59.25\$59.25
$60\$60
$70\$70
$79\$79
$80\$80
答案:D
知识点:逆推法
小提示:
$240\$240 包括三条原价轮胎和第四条的 $3\$3
The $240\$240 covers three tires at the regular price plus $3\$3 for the fourth
大提示:
先减去 $3\$3,再把剩下的钱平均分给三条原价轮胎
Subtract the $3,\$3, then divide the rest among the three full-price tires
解答:
三条原价轮胎共花 $240−$3=$237\$240 - \$3 = \$237。
所以一条轮胎的原价是 $2373=$79\dfrac{\$237}{3} = \$79。
所以正确答案是 D。
The three regular-price tires cost $240−$3=$237.\$240 - \$3 = \$237.
So one tire costs $2373=$79.\dfrac{\$237}{3} = \$79.
Thus, the correct answer is D .
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