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题库 / Prep2007E2-DS-171
If k is a positive integer and the tens digit of k + 5 is 4, what is the tens digit of k ?
(1) k > 35
(2) The units digit of k is greater than 5.
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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分析：（1），没有限定k个位数，则当k=41时，k+5=46，十位数为4；当k=36时，k+5=41，十位数为3，故无法确定。
（2）则直接限定了，如果个位数大于5（则为6,7,8,9），那么为了满足k+5的十位为4，只能使得k的十位数为3，加5后进一位为4.k的十位数就确定了，为3.
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