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M01#26 : Retired Discussions [Locked]

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Ok, first I do not think 1 is a prime number, you could check it out in materials but as far as I know it is not a prime number.

Back to the question

1. Multiple of a prime number : so it could be divided by itself, 1 and the prime number that make it => it is not a prime number

2. Product of 2 integer: 1 is also an integer, so if the number = 1 * an integer, it could be prime ( 1* 2 or 1*3) or could not an integer( 1*6) => stmt 2 not suff

1) x is a multiple of a prime number 2)x is a product of two integers

1 is not suff - x is multiple of prime number so x could be 3,6,9.... Now when x=3 x is prime else not. 2 is not suff - x could be product of any integers i.e. 2 and 3.

1+2 is also not suff - if x=3, x is product of two integers 1 and 3 but when x = 6, x is product of two integers 2 and 3. So still we do not know the exact value of x. Hence E is correct. _________________

If You're Not Living On The Edge, You're Taking Up Too Much Space

I don't see how B is suff - as X could be a product of 2 and 3 = 6 which is not a prime.

Not suff

Thats 3 integers. if x is a multiple of 2 integers, then x must be a prime.

Suppose: x = 2. it is a multiple of 1 and 2 i.e 2 integers. x = 3. it is a multiple of 1 and 3 i.e. 2 integers. x = 4. it is a multiple of 1, 2 and 4 i.e. 3 integers. x = 5. it is a multiple of 1 and 5 i.e. 2integers. x = 6. it is a multiple of 1, 2, 3 and 6 i.e. 4 integers.

x = 10. it is not a multiple of 2 and 5 rather its a multiple of 1, 2, 5, and 10.

Now I realize x could be -2. If so, x is a multi of either -2 and 1 or -1 and 2. If x = -2, x is not a prime.

So I think it should be C. From 1 and 2, x is a product of a prime and it is a product of 2 integers. In that case, x is a prime as it is multiple of a prime and 1.. _________________

Statement (1) says that x is a multiple of a prime number. Well, that immediately tells us that x is not a prime number because we can factor the a multiple. So now choices B, C, and E are eliminated.

Statement (2) says that x is a product of two integers. Well, we could look at the case of 2 * 3 = 6 but more importantly there is the case of 1 * any prime number. With the case of the 1 * prime number, choice D is eliminated.

Statement (1) says that x is a multiple of a prime number. Well, that immediately tells us that x is not a prime number because we can factor the a multiple. So now choices B, C, and E are eliminated.

Statement (2) says that x is a product of two integers. Well, we could look at the case of 2 * 3 = 6 but more importantly there is the case of 1 * any prime number. With the case of the 1 * prime number, choice D is eliminated.

Answer is A.

As far as I know, the general rule is that a number is a multiple of itself.

so 7*1 = 7 which is the first multiple of 7.

If one were to keep this rule in mind, then statement (1) would prove insufficient.

Thus, IMO, the correct answer is E. _________________

(1) Insufficient 2 * 3 = 6 – not a prime 1 * 3 = 3 – a prime (2) Insufficient 2*3*3 = 18 – not a prime 1*3 = 3 – a prime (1) and (2) 2*3*3 = 18 – not a prime 1*3 = 3 – a prime Thus, insufficient E

1) x is a multiple of a prime number 2)x is a product of two integers

The question is unclear particularly statement 1. I am assuming x could be a multiple of itself or something else.

1: x could be that prime number or a multiple of a prime number.

If x is a multiple of only itself and 1, it is a prime. If x is a multiple of integers other than 1 and itself, x is not a prime..

not suff...

2: x is a prime if x is a product of 2 integers i.e x and 1. suff.

B.

I don't agree on the the answer

Statement 2. Why don't we consider product of 2 integers as ANY Integer? ( the statement doesn't specify whether the integers are prime or not prime, for example: X can be a product of 1*2 ( then yes prime) but X can be a product of 2*3 ( thus not prime)

and statement 1 is enough as if X is multiple of prime numbers ( 2, 3, 5, ...) thus X is not prime because it will include 1* PRIME1*PRIME2 and thus has more than 2 factors!!!!

(1) Insufficient 2 * 3 = 6 – not a prime 1 * 3 = 3 – a prime (2) Insufficient 2*3*3 = 18 – not a prime 1*3 = 3 – a prime (1) and (2) 2*3*3 = 18 – not a prime 1*3 = 3 – a prime Thus, insufficient E

I have a question?!!! the statement 1 says- x is a multiple of prime numbers!!!! 1- is not a prime number , it is a FACTOR of prime number. the smalles prime number is 2 thus the combination of 1*3 will not hold true!

(1) Insufficient 2 * 3 = 6 – not a prime 1 * 3 = 3 – a prime (2) Insufficient 2*3*3 = 18 – not a prime 1*3 = 3 – a prime (1) and (2) 2*3*3 = 18 – not a prime 1*3 = 3 – a prime Thus, insufficient E

I have a question?!!! the statement 1 says- x is a multiple of prime numbers!!!! 1- is not a prime number , it is a FACTOR of prime number. the smalles prime number is 2 thus the combination of 1*3 will not hold true!

Please discuss!

Consider the below question from the same test where it;s clearly stated that 1- is not a prime number!

Is the product of x and y a prime number?

1. x^2 = 1 2. y is positive and prime; x is positive but not prime _________________

(1) Insufficient 2 * 3 = 6 – not a prime 1 * 3 = 3 – a prime (2) Insufficient 2*3*3 = 18 – not a prime 1*3 = 3 – a prime (1) and (2) 2*3*3 = 18 – not a prime 1*3 = 3 – a prime Thus, insufficient E

I have a question?!!! the statement 1 says- x is a multiple of prime numbers!!!! 1- is not a prime number , it is a FACTOR of prime number. the smalles prime number is 2 thus the combination of 1*3 will not hold true!

Please discuss!

Statement 1 says that "x is a multiple of a prime number." This is different from what you have quoted "x is a multiple of prime numbers"

Statement #1: x is a multiple of a prime number.

Consider Prime number 3. First multiple of 3 = 3 Second multiple of 3 = 6 Third multiple of 3 = 9,etc....

The statement says that: x is a multiple of a prime number. But now we don't know which multiple they are talking about! First? Second? Third?

If it is the first multiple, then x is a prime number. If it a the 2nd,3rd, etc, multiple, then no, x is not a prime number.

I think the best response to the question is option E. (1) x is a multiple of a prime no: 2 = 2x1; 6=2x3...Insuff (2) x is a product of two intgs: Again, 2=2x1; also 6 = 2x3 (two integers) so, Insufficient Considering (1) and (2): 2 = 2x1 is a multiple of a prime no & product of 2 integers...YES, x is prime -2 = -1 x 2: multiple of a prime(2) & product of 2 integers (2 & -1)...NO, x is not prime 6 = 2x3 is equally a multiple of a prime no and product of 2 integers..NO, x is not prime Therefore, (1) and (2) combined is out.

Option E seems the best. _________________

KUDOS me if you feel my contribution has helped you.

This means that x is a multiple of a prime. The primes are 2, 3, 5, 7, 11. So any multiples of these numbers are NOT prime. Therefore we know X is definately NOT PRIME.

How can a number be considered a multiple of itself ? i.e. 3 is a multiple of 3, 5 is a multple of 5 etc...

This means that x is a multiple of a prime. The primes are 2, 3, 5, 7, 11. So any multiples of these numbers are NOT prime. Therefore we know X is definately NOT PRIME.

How can a number be considered a multiple of itself ? i.e. 3 is a multiple of 3, 5 is a multple of 5 etc...

On the GMAT when we are told that a is divisible by b (or which is the same: "a is multiple of b", or "b is a factor of a"), we can say that: 1. a is an integer; 2. b is an integer; 3. \frac{a}{b}=integer.

So "a is multiple of b" means that \frac{a}{b}=integer --> the least positive multiple of an integer b is b itself as \frac{b}{b}=integer: 3 is a multiple of 3, 5 is a multiple of 5, ... (it's the same as the greatest factor of a positive integer is this integer itself.)

Catch here is to know that every prime number is a multiple of a prime number, that is the same number. 3 is a prime number and it is a multiple of 3 as 3*1=3.

This means that x is a multiple of a prime. The primes are 2, 3, 5, 7, 11. So any multiples of these numbers are NOT prime. Therefore we know X is definately NOT PRIME.

How can a number be considered a multiple of itself ? i.e. 3 is a multiple of 3, 5 is a multple of 5 etc...

As per definition of a "multiple", any number that allows any other number divide it completely (ie leaving zero as a remainder) is a multiple of that other number. 3, when divided by 3, leaves a remainder of 0, hence 3 is a multiple of 3. This applies to all numbers.

Additional info: 0 is also a multiple of all numbers as 0 when divided by any other number yields a remainder of 0. This is an important number property frequently tested on the GMAT. _________________