AMC10 2022 A

AMC10 2022 A · Q2

AMC10 2022 A · Q2. It mainly tests Rates (speed), Rounding & estimation.

Mike cycled $15$ laps in $57$ minutes. Assume he cycled at a constant speed throughout. Approximately how many laps did he complete in the first $27$ minutes?

Mike 骑车 57 分钟完成了 15 圈。假设他全程以恒定速度骑行。那么他在前 27 分钟大约完成了多少圈？

(A) 5 5

(B) 7 7

(D) 11 11

(E) 13 13

Answer

Correct choice: (B)

正确答案：（B）

Solution

Mike's speed is $\frac{15}{57}=\frac{5}{19}$ laps per minute. In the first $27$ minutes, he completed approximately $\frac{5}{19}\cdot27\approx\frac{1}{4}\cdot28=\boxed{\textbf{(B) } 7}$ laps.

Mike 的速度是 $\frac{15}{57}=\frac{5}{19}$ 圈/分钟。在前 27 分钟，他完成了大约 $\frac{5}{19}\cdot27\approx\frac{1}{4}\cdot28=\boxed{\textbf{(B) } 7}$ 圈。

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