If a needle is thrown at random on a sheet of paper (ruled with lines whose distance apart is exactly equal to the length of the needle) , how often can it be expected to fall on a line and how often into a blank space?

• 如果一根针被随意扔在一张纸上，并且规定纸边离针两端的距离相等，有多大几率指望针落在边上又有多大几率它落在空白处?