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Sunny143
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 07 Jun 2008, 12:49
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Is n/18 an integer?

(1) 5n/18 is an integer

(2) 3n/18 is an integer.



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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 07 Jun 2008, 12:56
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A

1) 5/18 is not an integer. As 5n/18 is an integer, n/18 must be an integer

2)If n=3, the answer is no
If n=6, the answer is YES. So NOT SUF
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 07 Jun 2008, 13:36
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Sunny143
Is n/18 an integer?

(1) 5n/18 is an integer

(2) 3n/18 is an integer.
Show more

1) n can be 18/5 (non integer) or 18 (integer) making n/18 into integer or non integer
not sufficient

2) n can be 6 ,12 ,18 etc making n/18 = intger or non integer

1)2) 15n/18 is an integer

--> n = 18/15, 36/15, 54/15, 72/15, 90/15 ... , 15*18/18
n/18 = non int , non int, .non int, non int, ..., int
insuff

ans = E
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 07 Jun 2008, 16:54
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Sunny143
Is n/18 an integer?

(1) 5n/18 is an integer

(2) 3n/18 is an integer.
Show more

I think the quesiton stem should include - n is an integer - or something like that.
if such info is actually present then it is A!

if not, then it is E, and the question would fall into the "cheap trick" category.... yuck!
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 07 Jun 2008, 17:40
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anirudhoswal
Sunny143
Is n/18 an integer?

(1) 5n/18 is an integer

(2) 3n/18 is an integer.

I think the quesiton stem should include - n is an integer - or something like that.
if such info is actually present then it is A!

if not, then it is E, and the question would fall into the "cheap trick" category.... yuck!
Show more

The question is from MGMAT...and there is no information missing....try to solve the problem rather than giving comments like the "cheap trick" category.... yuck ...this is totally uncalled for....

In fact E is not the OA. Thanks
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 08 Jun 2008, 00:26
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Sunny143
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Sunny143
Is n/18 an integer?

(1) 5n/18 is an integer

(2) 3n/18 is an integer.

I think the quesiton stem should include - n is an integer - or something like that.
if such info is actually present then it is A!

if not, then it is E, and the question would fall into the "cheap trick" category.... yuck!

The question is from MGMAT...and there is no information missing....try to solve the problem rather than giving comments like the "cheap trick" category.... yuck ...this is totally uncalled for....

In fact E is not the OA. Thanks
Show more

Hey.. don't take it personally man.
I did solve the question. Only, trying to illustrate that this problem is not really based on mathematical concepts... it is designed to catch you off-guard during the test.
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an Updated on: 08 Jun 2008, 22:29
Originally posted by ritula on 08 Jun 2008, 01:12.
Last edited by ritula on 08 Jun 2008, 22:29, edited 1 time in total.
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I will go with A
(1) 5n/18 is an integer. Since 5/18 is not an integer so n must be divisible by 18.
Sufficient
(2) 3n/18 is an integer. say n=6 then 3*6=18 is divisible by 18 but 6/18 is not an integer.
Insufficient
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 08 Jun 2008, 01:39
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ritula
I will go with A
(1) 5n/18 is an integer. Since 5/18 is not an integer so n must be divisible by n.
Sufficient
(2) 3n/18 is an integer. say n=6 then 3*6=18 is divisible by 18 but 6/18 is not an integer.
Insufficient
Show more

A should not be OA, If n=18/5, 5n/18 is integer, but n/18 is not integer :-D

If not E, C should be OA. I am tired of..!
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 08 Jun 2008, 16:01
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OA is C.

This is the OE from MGMAT:

(1) INSUFFICIENT: We are told that 5n/18 is an integer. This does not allow us to determine whether n/18 is an integer. We can come up with one example where 5n/18 is an integer and where n/18 is NOT an integer. We can come up with another example where 5n/18 is an integer and where n/18 IS an integer.

Let's first look at an example where 5n/18 is equal to the integer 1.
If 5n/18 = 1, then n/18 = 1/5 . In this case n/18 is NOT an integer.

Let's next look at an example where 5n/18 is equal to the integer 15.

If 5n/18 = 15, then n/18 = 3 . In this case n/18 IS an integer.

Thus, Statement (1) is NOT sufficient.

(2) INSUFFICIENT: We can use the same reasoning for Statement (2) that we did for statement (1). If 3n/18 is equal to the integer 1, then n/18 is NOT an integer. If 3n/18 is equal to the integer 9, then n/18 IS an integer.

The first possible value of n is 18, since this is the first value of n that ensures that both 5n/18 and 3n/18 are integers. If n = 18, then n/18 is an integer. Another possible value of n is 36. (This value also ensures that both 5n/18 and 3n/18 are integers). If n = 36, then n/18 is an integer.

(1) AND (2) SUFFICIENT: If 5n/18 and 3n/18 are both integers, n/18 must itself be an integer. Let's test some examples to see why this is the case.

A pattern begins to emerge: the fact that 5n/18 AND 3n/18 are both integers limits the possible values of n to multiples of 18. Since n must be a multiple of 18, we know that n/18 must be an integer. The correct answer is C.

Another way to understand this solution is to note that according to (1), n = (18/5)*integer, and according to (2), n = 6*integer. In other words, n is a multiple of both 18/5 and 6. The least common multiple of these two numbers is 18. In order to see this, write 6 = 30/5. The LCM of the numerators 18 and 30 is 90. Therefore, the LCM of the fractions is 90/5 = 18.

Again, the correct answer is C.
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 09 Jun 2008, 11:22
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Sunny143
OA is C.

This is the OE from MGMAT:

(1) INSUFFICIENT: We are told that 5n/18 is an integer. This does not allow us to determine whether n/18 is an integer. We can come up with one example where 5n/18 is an integer and where n/18 is NOT an integer. We can come up with another example where 5n/18 is an integer and where n/18 IS an integer.

Let's first look at an example where 5n/18 is equal to the integer 1.
If 5n/18 = 1, then n/18 = 1/5 . In this case n/18 is NOT an integer.

Let's next look at an example where 5n/18 is equal to the integer 15.

If 5n/18 = 15, then n/18 = 3 . In this case n/18 IS an integer.

Thus, Statement (1) is NOT sufficient.

(2) INSUFFICIENT: We can use the same reasoning for Statement (2) that we did for statement (1). If 3n/18 is equal to the integer 1, then n/18 is NOT an integer. If 3n/18 is equal to the integer 9, then n/18 IS an integer.

The first possible value of n is 18, since this is the first value of n that ensures that both 5n/18 and 3n/18 are integers. If n = 18, then n/18 is an integer. Another possible value of n is 36. (This value also ensures that both 5n/18 and 3n/18 are integers). If n = 36, then n/18 is an integer.

(1) AND (2) SUFFICIENT: If 5n/18 and 3n/18 are both integers, n/18 must itself be an integer. Let's test some examples to see why this is the case.

A pattern begins to emerge: the fact that 5n/18 AND 3n/18 are both integers limits the possible values of n to multiples of 18. Since n must be a multiple of 18, we know that n/18 must be an integer. The correct answer is C.

Another way to understand this solution is to note that according to (1), n = (18/5)*integer, and according to (2), n = 6*integer. In other words, n is a multiple of both 18/5 and 6. The least common multiple of these two numbers is 18. In order to see this, write 6 = 30/5. The LCM of the numerators 18 and 30 is 90. Therefore, the LCM of the fractions is 90/5 = 18.

Again, the correct answer is C.
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Okay.. I feel like taking all my comments back now. Good question sunny143.
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Is n/18 an integer? (1) 5n/18 is an integer (2) 3n/18 is an 10 Jun 2008, 08:11
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Sunny143
Is n/18 an integer?

(1) 5n/18 is an integer

(2) 3n/18 is an integer.
Show more

Very good question Sunny

this one got me.

was just tricked by A

newaz just need to be more careful
thanks for posting this ...kudos to u



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