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John took a test that had 60 questions numbered from 1 to 60  [#permalink]

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Difficulty:   5% (low)

Question Stats: 87% (01:10) correct 13% (00:54) wrong based on 614 sessions

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The Official Guide For GMAT® Quantitative Review, 2ND Edition

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 5/6 of the odd-numbered questions correctly and 4/5 of the even-numbered questions correctly.

Data Sufficiency
Question: 29
Category: Arithmetic Fractions
Page: 155
Difficulty: 600

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Re: John took a test that had 60 questions numbered from 1 to 60  [#permalink]

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SOLUTION

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 --> F = S + 7. Not sufficient.

(2) He answered 5/6 of the odd-numbered questions correctly and 4/5 of the even-numbered questions correctly. Since there are 30 odd-numbered questions and 30 even-numbered questions, then the number of questions answered correctly is 5/6*30 + 4/5*30. Sufficient.

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Re: John took a test that had 60 questions numbered from 1 to 60  [#permalink]

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4
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 5/6 of the odd-numbered questions correctly and 4/5 of the even-numbered questions correctly.

(1) Insufficient : He may have answered 2 correctly in the second half and therefore 9 in the first half . So, he could have answered 11correct. Similarly, 3 in the second half and therefore 10 in the first half . so, the result will be 13. Two different answers so (1) is not sufficient.

(2) Sufficient : Given that we know the total number of the questions and also how many odd and how many even there are, the question turns into simple multiplication.

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GMAT 1: 590 Q45 V27 Re: John took a test that had 60 questions numbered from 1 to 60  [#permalink]

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No. of questions answered correctly = ?

(1). FC = SC + 7;
Insufficient as there are 2 variables.

(2). Since the total no. of questions = 60, starting from 1, there will be 30 odd and 30 even questions.
Odd no. of questions correct = (5/6)*30 = 25;
Even no. of questions correct = (4/5)*30 = 24;

So, the total no. of questions answered correctly = 49.

Of course, we don't have to solve these for DS. If we know it is solvable, we can mark the answer and move on.

Ans is (B).
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Re: John took a test that had 60 questions numbered from 1 to 60  [#permalink]

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Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

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 5/6 of the odd-numbered questions correctly and 4/5 of the even-numbered questions correctly.

Statement 1) out of 30 questions, he answered x+7 and out of next 30 questions, he answered x questions, we still don't know x. Not Sufficient.
Statement 2) As even numbered and odd numbered questions will be mutually exclusive (no overlapping), we know there are 30 odd and 30 even questions.
So we can calculate the number of questions answered.

Hence Option B)
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Math Expert V
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Posts: 55681
Re: John took a test that had 60 questions numbered from 1 to 60  [#permalink]

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SOLUTION

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 --> F = S + 7. Not sufficient.

(2) He answered 5/6 of the odd-numbered questions correctly and 4/5 of the even-numbered questions correctly. Since there are 30 odd-numbered questions and 30 even-numbered questions, then the number of questions answered correctly is 5/6*30 + 4/5*30. Sufficient.

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John took a test that had 60 questions numbered from 1 to 60  [#permalink]

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Bunuel wrote:
SOLUTION

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 --> F = S + 7. Not sufficient.

(2) He answered 5/6 of the odd-numbered questions correctly and 4/5 of the even-numbered questions correctly. Since there are 30 odd-numbered questions and 30 even-numbered questions, then the number of questions answered correctly is 5/6*30 + 4/5*30. Sufficient.

does first half of the test mean there were 30 questions in the first half?

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_________________ John took a test that had 60 questions numbered from 1 to 60   [#permalink] 28 Nov 2018, 11:19
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