Difficult Math Question #27 - Series
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countingdolls
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abby_g
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both are enuf. My answer is D.
lets take 4 numbers. n, n+2, n+4, n+6
from 1, we have n+4 + n+6 = 30. Get the value of n and the numbers.
From 2, we have n+n+2 = 22. Get the value of n and the numbers.
Hence, d.
lets take 4 numbers. n, n+2, n+4, n+6
from 1, we have n+4 + n+6 = 30. Get the value of n and the numbers.
From 2, we have n+n+2 = 22. Get the value of n and the numbers.
Hence, d.
To err is human, to repeat it is criminal.
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anandsebastin
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D
The 4 consecutive even numbers are x, x+2, x+4, x+6
Statement 1:
x+4+x+6 =30
2x=20
x+6 = 16 SUFF
Statement 2:
x+x+2 = 22
2x=20
x+6=16 SUFF
The 4 consecutive even numbers are x, x+2, x+4, x+6
Statement 1:
x+4+x+6 =30
2x=20
x+6 = 16 SUFF
Statement 2:
x+x+2 = 22
2x=20
x+6=16 SUFF
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800guy
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here's the OA:
the ans is D
Soln: I guess, there are 4 consecutive even numbers to start with..
Stmt 1) Sum of 3rd even + Sum of 4th even = 30 => 14+16 = 30 => 4th even num = 16.. Sufficient
Stmt 2) Sum of Ist even +Sum of 2nd even = 22 => 10 and 12 are the 2 numbers to begin with, then 3rd num = 14 and 4th num = 16.. Sufficient
Ans – D
the ans is D
Soln: I guess, there are 4 consecutive even numbers to start with..
Stmt 1) Sum of 3rd even + Sum of 4th even = 30 => 14+16 = 30 => 4th even num = 16.. Sufficient
Stmt 2) Sum of Ist even +Sum of 2nd even = 22 => 10 and 12 are the 2 numbers to begin with, then 3rd num = 14 and 4th num = 16.. Sufficient
Ans – D
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countingdolls
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Find the fourth consecutive even number:
(I) the sum of the last two numbers is 30
(II) the sum of the first two numbers is 22
If, the above is all that is given as the q, then from (I), u CANNOT find which two number in the series result in a sum of 30 (8th & 9th or 15th & the 16th)...there in no way for you to figure that out. Thats why (I) is not enuf.
In the answers posted, its assumed that the 3rd & the 4th no add up to 30.
thats why B
Pls correct me if im mistaken
(I) the sum of the last two numbers is 30
(II) the sum of the first two numbers is 22
If, the above is all that is given as the q, then from (I), u CANNOT find which two number in the series result in a sum of 30 (8th & 9th or 15th & the 16th)...there in no way for you to figure that out. Thats why (I) is not enuf.
In the answers posted, its assumed that the 3rd & the 4th no add up to 30.
thats why B
Pls correct me if im mistaken
CountingDolls: you said "u CANNOT find which two number in the series result in a sum of 30 (8th & 9th or 15th & the 16th)" but if you read the question again you should notice that:
(1) tells you that the LAST TWO numbers sum is 30.
(2) tells you that the FIRST TWO numbers sum is 22.
So you shouldn't have to worry about the 8th, 9th or other numbers. Also, the question implies that there are only four numbers in the series.
(1) tells you that the LAST TWO numbers sum is 30.
(2) tells you that the FIRST TWO numbers sum is 22.
So you shouldn't have to worry about the 8th, 9th or other numbers. Also, the question implies that there are only four numbers in the series.
Thank you,
Ken
Ken
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countingdolls
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Hi khilker,
(1) tells you that the LAST TWO numbers sum is 30.
since we do not know how many numbers are there in the series, its not enough to find the answer.
Also, how does the question imply that there are only four numbers in the series?
Using what is given, assuming nothing, u cant conclude that tehre are just 4 nos in the series.
Isnt it not right to assume that there are just 4 numbers?
Could we discuss this because for me its out and out B?
Would some expert please comment
thanks
(1) tells you that the LAST TWO numbers sum is 30.
since we do not know how many numbers are there in the series, its not enough to find the answer.
Also, how does the question imply that there are only four numbers in the series?
Using what is given, assuming nothing, u cant conclude that tehre are just 4 nos in the series.
Isnt it not right to assume that there are just 4 numbers?
Could we discuss this because for me its out and out B?
Would some expert please comment
thanks
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rajs.kumar
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I agree with counting dolls, and I arrived at answer B.
The question stem just asks for the fourth consecutive even number. 14 and 16 could any two.
For example 2, 4, 6, 8, 10, 12, 14, 16. In this case 14 and 16 are the last two and not necessarily the fourth.
The question stem just asks for the fourth consecutive even number. 14 and 16 could any two.
For example 2, 4, 6, 8, 10, 12, 14, 16. In this case 14 and 16 are the last two and not necessarily the fourth.
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ajith
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I agree thererajs.kumar wrote:I agree with counting dolls, and I arrived at answer B.
The question stem just asks for the fourth consecutive even number. 14 and 16 could any two.
For example 2, 4, 6, 8, 10, 12, 14, 16. In this case 14 and 16 are the last two and not necessarily the fourth.
Part of the difficulty with this problem is that it is NOT written in a GMAC way.
Statement I is insufficient, for the previously mentioned reasons.
I think that it is important to work with actual GMAC questions (or questions that are closely modeled on GMAC style). My point is NOT that one can't learn from a problem like this one, but that the question-writer imposes ambiguities on the question in a way that is very different from what GMAC does.
There is ambiguity as to whether the set is limited to four terms. Having said that, this problem never even mentioned that the terms are part of a set. GMAC doesn't do this.Find the fourth consecutive even number:
(I) the sum of the last two numbers is 30
(II) the sum of the first two numbers is 22
Statement I is insufficient, for the previously mentioned reasons.
I think that it is important to work with actual GMAC questions (or questions that are closely modeled on GMAC style). My point is NOT that one can't learn from a problem like this one, but that the question-writer imposes ambiguities on the question in a way that is very different from what GMAC does.
Ian Streicher
GMAT/MBA Expert
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beatthegmat
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Well said, Ian. Nothing beats working with OG as your primary practice sets, since it allows you to learn the GMAC way.
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