GMAT申友数据充分DS题库-Beginning in January of last year, Carl made deposits of $120 into his account on the 15th of each month-精选题库-真题答案解析

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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.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

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答案：

已知从去年

1月开始，Carl每个月的15号存入120美元到它的账户，一直到某一个月，它开始在每个月的5号开始取钱，每次取50美元。去年的账户没有其他的交易，问如果在去年5月它的账户余额为2600，那么是否可以求出去年账户里每月金额变动的范围是多少？条件一说的是4月它账户里的余额比2625少，那么如果在5月15是取了50，那么5月底的账户金额不可能是2600，所以只能是存，那么4月期末的账户余额是2480，5月之前都是存钱，也就是说5月以前的账户余额都是可以确定的，但是5月以后的月份，我们却无法判断它是取是存，所以不充分。条件二说的是它6月的账户余额少于2675，所以我们可以判断在6月15日开始取款，这样才能使它6月的账户余额少于2675，即2550.但5月之前的，我们无法判断是存是取，所以不充分。（1）和（2）联立，可以求得5月15日存款，6月15日取款，即1月-5月都是存款，6月-12月为取款，一共存款5个月，取款7个月。可求1月期末余额为2120（原始金额2000，1月15日存入120），12月期末余额为2250，比较后1月期末余额更小，及最小值为2120，Range是2600-2120=480。所以选C