AMC8 2018

AMC8 2018 · Q12

AMC8 2018 · Q12. It mainly tests Rates (speed), Interest / growth (simple).

The clock in Sri’s car, which is not accurate, gains time at a constant rate. One day as he begins shopping he notes that his car clock and his watch (which is accurate) both say 12:00 noon. When he is done shopping, his watch says 12:30 and his car clock says 12:35. Later that day, Sri loses his watch. He looks at his car clock and it says 7:00. What is the actual time?

Sri车上的钟不准确，以恒定速率快走。有一天他开始购物时，注意到他的车钟和他的手表（准确的）都显示12:00中午。购物结束后，他的手表显示12:30，车钟显示12:35。那天晚些时候，Sri丢了手表。他看车钟显示7:00，实际时间是几点？

(A) 5:50 5:50

(B) 6:00 6:00

(D) 6:55 6:55

(E) 8:10 8:10

Answer

Correct choice: (B)

正确答案：（B）

Solution

Answer (B): The ratio of time as measured by Sri’s car clock to actual time is $\frac{35}{30}=\frac{7}{6}$. Therefore when the clock shows that $7$ hours have passed since noon, only $6$ hours have actually passed, so the actual time is $6$:00.

答案（B）：Sri 的车钟所测量的时间与实际时间之比为 $\frac{35}{30}=\frac{7}{6}$。因此，当车钟显示从中午起已经过去 $7$ 小时时，实际上只过去了 $6$ 小时，所以实际时间是 $6$:00。

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