OG数学 DS161题

ozymendias

Beginning in January of last year，Carl made deposits of $120 into his account on the 15th of each month for several consecutive months and then made withdrawals of $50 from the account on the 15th of each of the remaining months of last year. There were no other transactions in the account last year. If the closing balance of Carl's account for May of last year was $2,600, what was the range of the monthly closing balances of Carl's account last year?

(1) Last year the closing balance of Carl's account for April was less than $2,625

(2) Last year the closing balance of Carl's account for June was less than $ 2,675

这题答案选C~请指教！谢谢~~

ozymendias

谢谢。。。。。。。

zhangluE

题目的意思是要一年之中前面连续几个月一直往户头上存钱，每月是120，后面的几个月一直从户头上取钱，每月是50.题目要求每月户头的range~所以我们要判断出前面哪几个月是一直存钱的。
（1）从条件1可以看出来，5月份是往户头里存钱的，但我们不知道啥时后取钱，所以insufficient
(2) 从条件2可以看出，6月份是从户头里取钱，但不知道从啥时候开始取的，是5月？4月？所以Insufficient
结合条件1和条件2，前5个月一直往户头存钱，后面一直取钱，很容易就算出range啦~所以应该选C~

victoria820

这个题目我想怎么不用管利率吗？