Test Code 52, section4, Question 8

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irfan_m1973: Junior | Next Rank: 30 Posts; Posts: 18; Joined: Fri Nov 13, 2009 6:27 amFollowed by: 1 member

by irfan_m1973 » Sun Dec 06, 2009 9:39 pm

Dan took a 20-question multiple-choice test in psychology. If Dan answered every question, did he answer at least 12 questions correctly?

(1) Dan answered fewer than 40 percent of the questions incorrectly.
(2) Dan answered at least 25 percent of the questions incorrectly.

OA is C (BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient)

PLS explain

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Source: Beat The GMAT — Data Sufficiency | Sun Dec 06, 2009 9:39 pm

Testluv: GMAT Instructor; Posts: 1302; Joined: Mon Oct 19, 2009 2:13 pmFollowed by: 164 members; Location: Toronto; Thanked: 539 times; GMAT Score:800

by Testluv » Sun Dec 06, 2009 10:12 pm

Assuming you've transcribed the question properly, the correct answer should be choice A.

We are asked whether he answered at least 12 questions correctly, and there are 20 questions on the test.

(1) Dan answered fewer than 40 percent of the questions incorrectly.

Because 40 percent of 20 is 8, we can read this statement as: "Dan answered fewer than 8 questions incorrectly". If Dan answered fewer than 8 incorrectly, then that means he answered at least 12 correctly.

Sufficient.

(2) Dan answered at least 25 percent of the questions incorrectly.

25 percent of 20 is 5. So we can read this statement as "Dan answered at least 5 questions incorrectly". Then, that means he answered at most 15 questions correctly.

So, that could mean he answered 5 correctly or 15 correctly.

Insufficient.

Choose A.

Kaplan Teacher in Toronto

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irfan_m1973: Junior | Next Rank: 30 Posts; Posts: 18; Joined: Fri Nov 13, 2009 6:27 amFollowed by: 1 member

by irfan_m1973 » Sun Dec 06, 2009 10:20 pm

Testluv wrote:Assuming you've transcribed the question properly, the correct answer should be choice A.

We are asked whether he answered at least 12 questions correctly, and there are 20 questions on the test.

(1) Dan answered fewer than 40 percent of the questions incorrectly.

Because 40 percent of 20 is 8, we can read this statement as: "Dan answered fewer than 8 questions incorrectly". If Dan answered fewer than 8 incorrectly, then that means he answered at least 12 correctly.

Sufficient.

(2) Dan answered at least 25 percent of the questions incorrectly.

25 percent of 20 is 5. So we can read this statement as "Dan answered at least 5 questions incorrectly". Then, that means he answered at most 15 questions correctly.

So, that could mean he answered 5 correctly or 15 correctly.

Insufficient.

Choose A.

Thank you. I overlooked the answer in the OA. It is indeed A. Thanks yet again.

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