这题balance怎么说，有点懵~

frankzhiwei · 发表于 2010-9-18 12:59:00

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 billing 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.

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【答案】D

求解释，请尽量详尽~主要是看不懂那个是怎么过分算法！

panovation · 发表于 2010-9-18 16:19:27

我尝试一下，你看看这样解释行不，balance 就是账户的结余，那么如题所示Jane 这个月开始的户头上有600 刀，如果她这个月都不消费，这个月的average balance 就会使600，题目说了她这个消费了300，但因为没有说什么时候消费的，所以整个月的average balance 求不出，因为average balance = day 1 balance+day 2 balance+day 3 balance。。。。day 30 balance /30
1）因为知道payment 是21 号给的，所以前面20天的balance 都是600，后面开始就是300，这个就可以算了
2）因为jane 这个月除了那300，都没进行过其他消费了，540比600小，就是在这个月某一天消费了这300，那么得志25th 号之后的balance 也会是540。所以整个月的average balance 就是540
所以D ，希望能帮助你理解

这题balance怎么说，有点懵~

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