Question

Elisa 在泳池里游圈。刚开始时，她用 $25$ 分钟游完 $10$ 圈。现在她能用 $24$ 分钟游完 $12$ 圈。她每圈用时减少了多少分钟？

Elisa swims laps in the pool. When she first started, she completed $10$ laps in $25$ minutes. Now, she can finish $12$ laps in $24$ minutes. By how many minutes has she improved her lap time?

$\dfrac{1}{2}$

$\dfrac{3}{4}$

$1$

$2$

$3$

答案：A

知识点：速率

难度评级：560

解答：

起初 Elisa 每圈用 $25/10=2.5$ 分钟。现在她每圈用 $24/12=2$ 分钟。

因此每圈用时减少 $2.5-2=0.5=\dfrac{1}{2}$ 分钟。

所以正确答案是 A。

Initially, Elisa swam one lap in $25/10=2.5$ minutes. Now she swims one lap in $24/12=2$ minutes.

Therefore, she improved her lap time by $2.5-2=0.5=\dfrac{1}{2}$ minute.

Thus, A is the correct answer.

2006 AMC 8 第 3 题

答案：A

难度评级：560

解答：

其他年份的第 3 题