C 比，比率relation between two amounts determined by the number of times one contains the other

　show a ～ of...to...　比率为…比…
　direct〔inverse〕～　正〔反〕比
　birth〔death〕～　出生〔死亡〕率
　current ～　电流比
　at the ～　按比率
　by a ～ of　根据…的比率
　in direct ～　按正比率
　with the ～ of　以…比率
　～ between　两者之间的比
　～ of...to...　…与…之比
　～ to　对…的比率

　The ratio of pupils to teachers was 30 to 1.　学生和老师的比率是30比1。
　The ratios of 1 to 5 and 20 to 100 are the same. 　1与5之比和20与100之比相同。

　［词源］拉丁语ratio（比，比率）