With an appropriate preposition: (1)We left Xi'an ____ a very ho

With an appropriate preposition:
(1)We left Xi'an ____ a very hot summer afternoon. (2)The number of the employees has grown from 1, 000 to 1, 200. This means it has risen ____ 20 percent.

【正确答案】：on;by
【题目解析】：【考点点击】本题考查介词。【要点透析】在具体的某一天或某一天的上下午,要用on来表示; percent前常用by,表示上升与下降的百分比。