一辆汽车开往距离出发地180千米的目的地，出发后第一小时内按原计划的速度匀速行驶，一小时后以原来速度的1.5倍匀速行驶，并比原计划提前40分到达目的地．求前一小时的行驶速度．

有无耳垂是一对相对性状，如表数据是对部分家庭的遗传情况调查，请回答问题：

一个正多边形绕它的中心旋转45°后，就与原正多边形第一次重合，那么这个正多边形（　　）

阅读理解 阅读下列短文，选出最佳答案。

    “I will think of it.” It is easy to say this, but do you know what great things have come from thinking?

    Sir Isaac Newton was sitting in his garden when he saw an apple fall from a tree. He began to think and tried to find out why the apple fell. Then he discovered how the sun, moon, and stars are kept in their places.

    A boy named James Watt sat quietly by the fire, watching the lid of the kettle move up and down. He wanted to find out why the steam in the kettle moved the lid. From that time he went on thinking and thinking. And when he became a man, he improved the steam engine (蒸汽机) so much that it could easily do the work of many horses.

     James Ferguson was a poor boy. Once, seeing the inside of a watch, he wondered. “Why should I not make a watch?” But how could he get the materials to make the mainspring (钟表的主发条)? He soon found he could make it with whalebone (鲸骨). He then made a wooden clock which kept good time. His motto (座右铭) was “I will think of it.” And he made his thoughts useful to himself and the world. 

    Boys and girls, when you have a difficult lesson to learn, don't lose heart, and don't ask someone for help before helping yourselves. Think, and by thinking you will learn how to think to some purpose.