题目

Last year a credit card company gave each of its cardholders a rebate on the amount charged during the year. The rebate was 1 percent of the portion of the amount charged in excess of $2,000 but less than or equal to $5,000, and 2 percent of the portion of the amount charged in excess of $5,000. If a cardholder received a total rebate equal to 1.3 percent of the amount charged, how much did the cardholder charge on the card?

选项

A.

$6,000

B.

$7,000

C.

$8,000

D.

$9,000

E.

$10,000

解析

去年一家信用卡公司给它的每位持卡人在当年的消费金额上提供回扣。对于消费金额超过2000美元但小于等于5000美元的部分,回扣为该部分金额的1%;对于消费金额超过5000美元的部分,回扣为该部分金额的2%。如果一位持卡人收到的总回扣等于其消费金额的1.3%,那么这位持卡人的信用卡消费金额是多少? 设持卡人的消费金额为\(x\)美元(\(x>5000\)) 对于消费金额在\(2000\)到\(5000\)之间的部分,即\(5000 - 2000=3000\)美元,这部分的回扣为\(3000\times1\% = 30\)美元 对于超过\(5000\)美元的部分为\((x - 5000)\)美元,这部分的回扣为\((x - 5000)\times2\%\) 总回扣等于消费金额的\(1.3\%\),即\(0.013x\) 则可列出方程:\(30+(x - 5000)\times0.02=0.013x\) \[ \begin{align*} 30+(x - 5000)\times0.02&=0.013x\\ 30 + 0.02x-100&=0.013x\\ 0.02x-0.013x&=100 - 30\\ 0.007x&=70\\ x&=10000 \end{align*} \] 所以,持卡人的信用卡消费金额是\(10000\)美元,答案是E。
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