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题库 / GMATLA-DS-12
Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she buy?
(1) She bought $4.40 worth of stamps.
(2) She bought an equal number of $0.15 stamps and $0.29 stamps.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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忽略了一个潜在的条件，邮票数x和y都为整，试数
15的倍数个位只可能是0或5；9的倍数就多了0到9都可能
假设15x个位是5，9y的个位就只能是5，y＝5，检验不可能得到x为整；y＝15，已经比440多了，排除
15x的个位只能是0，9y的个位只能0，y不能是0，y＝10只有一种可能
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