题目

Today, roller skating （滑旱冰）is easy and fun. But a long time ago, it wasn't easy at all. Before 1750, the idea of skating didn't exist. That changed because of a man named Joseph Merlin. Merlin's work was making musical instruments. In his spare time he liked to play the violin. Joseph Merlin was a man of ideas and dreams. People called him a dreamer. One day Merlin received an invitation（邀请） to attend a fancy dress ball（舞会）. He was very pleased and a little excited. As the day of the party came near, Merlin began to think how to make a grand entrance at the pa圆的周长总是直径直径的三倍多一点，这个倍数是个无限不循环无限不循环的数，叫做圆周率圆周率．