一列火车由某站以60km/h的平均速度开出10min后，一辆汽车去追赶

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问题计算题

一列火车由某站以60km/h的平均速度开出10min后，一辆汽车去追赶这列火车，为了在15min以内追上这列火车，那么这辆汽车的平均速度不能小于多少？

答案

解析：x_汽=x_火+x₀，x₀为开始阶段火车10min的路程

有v_汽×h=60km/h×()h，即v_汽为100km/h

选择题

— Where is Sue? I haven't seen her for a long time.

— I heard she ______ a businessman and moved to Japan last month. [ ]

A. married

B. married to

C. get married

D. was married with

单项选择题

计算由曲面及z=x²+y²所围成的立体体积的三次积分为（）。