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chondro48
Hi TheNightKing,
This explanation may enlighten you.

Known: n is a positive integer.

Is n a multiple of 121? --> basically, the question is whether n has double factor of 11.

(1) 44 is the greatest common divisor (GCD) of 220 and n
From this statement, we understand that \(44(=11*2^2)\) is a factor of n. However, we can only deduce that n has single, double, or even more factor(s) of 11. Examples:
1) 44 is the GCD of 220 and n= 44 --> is n a multiple of 121? NO, n has only single factor of 11.
2) 44 is the GCD of 260 and n= 44*11 = 484 --> is n a multiple of 121? YES, n has double factors of 11.
NOT SUFFICIENT

(2) 968 is the least common multiple (LCM) of 121 and n
Since \(968=8*121=8*11^2\) and 121 has double factor of 11, then n could have zero, single factor, or even double factor of 11. Example:
1) 968 is the LCM of 121 and n= 8 --> n isn't a multiple of 121, since n has zero factor of 11.
2) 968 is the LCM of 121 and n= 8*11 = 88 --> n isn't a multiple of 121, since n has only single factor of 11.
3) 968 is the LCM of 121 and n= 8*11*11 = 968 --> n is a multiple of 121, since n has double factor of 11.
NOT SUFFICIENT

Combining (1) and (2)
From both statements, we can only deduce that n has either single or double factor(s) of 11:
Case #1. n has only single factor of 11 and thus, isn't a multiple of 121.
\(n= 8*11 = 88\) --> 44 is the GCD of 220 and 88 (OK) --> 968 is the LCM of 121 and 88 (OK)
Case #2. n has double factor of 11 and thus, is a multiple of 121.
\(n= 8*11*11 = 968\) --> 44 is the GCD of 220 and 968 (OK) --> 968 is the LCM of 121 and 968 (OK)
NOT SUFFICIENT

Answer is (E)

I could not have asked for anything better than this. Thank you for taking time out to type all this. I will bookmark your response and Kudos to you!
Thank you
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chondro48
If n is a positive integer, is n a multiple of 121?

(1) 44 is the greatest common divisor of 220 and n
(2) 968 is the least common multiple of 121 and n

+1 kudo, if this is deemed worthy of 700-level.

Okay, a pretty challenging question (+1 kudos). took about 3 minutes. What is the source?

Basically the question is asking whether \(\frac{n}{121}\)=integer or \(\frac{n}{11*11}\)=integer?

statement (1): 44 is the greatest common divisor of 220 and n
220= 2x2x5x11
n= 2x2x11 (minimum numbers that n must have since GCD = 44=2*2*11).
other than the above given values(must) of n, other additional values could be 2^anything x any number x 11^anything.

if n=2*2*11=44, then is \(\frac{44}{121}\)=integer? NO
if n=2*2*2*5*11= 440 NO
but if n=2*2*11*11=484, then is \(\frac{484}{121}\)=integer?YES!

Different answers. INSUFFICIENT!

statement (2):968 is the least common multiple of 121 and n
LCM=968=2x2x2x11x11
121=11*11
n= 2x2x2 or 2x2x2x11 or 2x2x2x11x11

if n= 2x2x2=8, then is \(\frac{8}{121}\)=integer? NO
if n=2x2x2x11=88, then is \(\frac{88}{121}\)=integer? NO
if n=2x2x2x11x11, then is \(\frac{(2*2*2*11*11)}{(11*11)}\)? YES!

Different answers. INSUFFICIENT!

Statement 1+2
If you notice, same values were tested in each statements. Indirectly, both the statements were similar. Different answers. INSUFFICIENT!

thus, answer is option E
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chondro48
If n is a positive integer, is n a multiple of 121?

(1) 44 is the greatest common divisor of 220 and n
(2) 968 is the least common multiple of 121 and n

+1 kudo, if this is deemed worthy of 700-level.


Asked: If n is a positive integer, is n a multiple of 121?

(1) 44 is the greatest common divisor of 220 and n
\(220 =2^2.5.11\)
\(44 = 2^2.11\)
n = 44k where k is an integer
If n =44 => 44 is the greatest common divisor of 220 and n but n is NOT a multiple of 121
But if n=484 => 44 is the greatest common divisor of 220 and n and n is a multiple of 121
NOT SUFFICIENT

(2) 968 is the least common multiple of 121 and n
\(968 = 2^3.11^2\)
\(121 = 11^2\)
n = 2^3k=8k where k is an integer
If n =8 => 968 is the least common multiple of 121 and n but n is NOT a multiple of 121
But if n=968 => 968 is the least common multiple of 121 and n and n is a multiple of 121
NOT SUFFICIENT

Combining (1) & (2)
(1) 44 is the greatest common divisor of 220 and n
\(220 =2^2.5.11\)
\(44 = 2^2.11\)
n = 44k where k is an integer
(2) 968 is the least common multiple of 121 and n
\(968 = 2^3.11^2\)
\(121 = 11^2\)
\(n = 2^3m=8m\) where m is an integer
n=88t where t is an integer
If n=88 => n is NOT a multiple of 121
But if n=968 => n is a multiple of 121
NOT SUFFICIENT

IMO E
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