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题库 / OG2017Q-DS-238
John took a test that had 60 questions numbered from 1 to 60. How many of the questions did he answer correctly?
(1) The number of questions he answered correctly in the first half of the test was 7 more than the number he answered correctly in the second half of the test.
(2)He answered ~$5 \over 6$~ of the odd-numbered questions correctly and
~$4 \over 5$~ of the even-numbered questions correctly.
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.
题目分析：
（1） 根据条件1，前30个题比后30个题多答对了7道，但无法确定答对了多少道。
（2） 奇数号的题和偶数号的题均为30道，所以奇数号的题答对了~$\frac{5}{6}*30=25$~道，偶数号的题答对了~$\frac{4}{5}*30=24$~道，总共答对了25+24=49道，得解。
因此，本题答案为（B），仅条件2可以解题，条件1不行。
看一二选项的顺序。。。