John test qns

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kishokbabu: Senior | Next Rank: 100 Posts; Posts: 62; Joined: Wed May 04, 2011 9:50 pmFollowed by: 2 members; Thanked: 2 times

by kishokbabu » Wed Dec 28, 2011 6:29 pm

John took a test that had 60 qns numbered from 1 to 60. How many of the qns did he answer correctly?

a) The no of the qns he answered correctly in the first half of the test was 7 more than the no he answered correctly in the second half of the test.
b) He answered 5/6 of the odd numbered qns correctly and 4/5 of the even numbered questions correctly.

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Source: Beat The GMAT — Data Sufficiency | Wed Dec 28, 2011 6:29 pm

pemdas: Legendary Member; Posts: 1084; Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members; Thanked: 158 times

by pemdas » Wed Dec 28, 2011 7:18 pm

st(1) doesn't tell if he answered all questions in test, Insuff
st(2) Suff as it precisely states ratio and no if correct and incorrect questions

b

kishokbabu wrote:John took a test that had 60 qns numbered from 1 to 60. How many of the qns did he answer correctly?

a) The no of the qns he answered correctly in the first half of the test was 7 more than the no he answered correctly in the second half of the test.
b) He answered 5/6 of the odd numbered qns correctly and 4/5 of the even numbered questions correctly.

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neelgandham: Community Manager; Posts: 1060; Joined: Fri May 13, 2011 6:46 amFollowed by: 52 members; Location: Utrecht, The Netherlands; Thanked: 318 times

by neelgandham » Thu Dec 29, 2011 4:10 am

John took a test that had 60 qns numbered from 1 to 60. How many of the qns did he answer correctly?

a)The no of the qns he answered correctly in the first half of the test was 7 more than the no he answered correctly in the second half of the test.

let x be the number of questions answered correctly in the second half of the test, then x+7 is the number of questions answered correctly in the first half of the test. total number of questions answered correctly = 2x + 7. As we do not know the value of x, this statement is insufficient to answer the question

b)He answered 5/6 of the odd numbered qns correctly and 4/5 of the even numbered questions correctly.

Number of even numbered questions : 30
Number of odd numbered questions : 30
Number of even numbered questions answered correctly: (4/5)*30 = 24
Number of odd numbered questions answered correctly: (5/6)*30 = 25
Total number of questions answered correctly:49
Sufficient to answer the question

Answer :B

p.s: You need not solve for the values but the illustration above is for the benefit of fellow BTGers who are not comfortable solving DS problems.

Anil Gandham
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