请教两道数学题

sxcream

全是黄色OG上的。DS.

第一题是题目看不懂，看了答案之后我还是看不懂。请高人帮我指点迷津。

On Jane's credit card account,the average daily balance for a 30-day billing cycle is the average(arithmetic mean) of the daily balances at the end of each of the 30 days.At the beginning of a certain 30-day billing cycle,Jane's credit card account had a balance of $600.Jane made a payment of $300 on the account during the billing cycle.If no other amounts were added to or subtracted from the account during the billin cycle,what was the average daily balance on Jane's account for the billing cycle?

1,Jane's payment was credited on the 21st day of the billing cycle.

2,The average daily balance through the 25th day of the billing cycle was $540.

第二题是我对官方答案有异议。

Is n an integer?

1,n² is an integer

2,blablabla

答案是选B的，但是我觉得1也是对的啊。。。。如果N不是整数的话，N的平方怎么会是整数呢？

LemonDK

第二个题目 √2就排除了1了

第一个题目我也读不太明白，不好意思哦

等nn回答