求问三道prep题目。。。。

The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present . If the concentration of chemical B is increased by 100 present, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

40% increase

At a dinner party, 5 people are to be seated around a circular table. Two seating arrangements are considered different only when the positions of the people are different relative to each other. What is the total number of different possible seating arrangements for the group?

24

Alice's take-home pay last year was the same each month, and she saved the same fraction of her take-home pay each month. The total amount of money that she had saved at the end of the year was 3 times the amount of the portion of her monthly take-home pay that she did not save. If all the money that she saved last year was from her take-home pay, what fraction of her take-home pay did she save each month?

1/5
那啥。。。。第一题和第三题的题目不太明白。。。。。