AMC12 2004 B

AMC12 2004 B · Q5

AMC12 2004 B · Q5. It mainly tests Fractions, Ratios & proportions.

On a trip from the United States to Canada, Isabella took $d$ U.S. dollars. At the border she exchanged them all, receiving $10$ Canadian dollars for every $7$ U.S. dollars. After spending $60$ Canadian dollars, she had $d$ Canadian dollars left. What is the sum of the digits of $d$?

Isabella 从美国去加拿大旅行，带了 $d$ 美元。在边境她把钱全部兑换，按每 $7$ 美元换 $10$ 加元。花了 $60$ 加元后，她还剩 $d$ 加元。$d$ 的各位数字之和是多少？

(A) 5 5

(B) 6 6

(D) 8 8

(E) 9 9

Answer

Correct choice: (A)

正确答案：（A）

Solution

Isabella had $60+d$ Canadian dollars. Setting up an equation we get $d=\frac{7}{10}\cdot(60+d)$, which solves to $d=140$, and the sum of digits of $d$ is $\boxed{\mathrm{(A)}\ 5}$.

Isabella 一共有 $60+d$ 加元。列方程得 $d=\frac{7}{10}\cdot(60+d)$，解得 $d=140$，因此 $d$ 的各位数字之和为 $\boxed{\mathrm{(A)}\ 5}$。

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