what would be the easiest way to solve this type of problem?
If w is a prime number greater than 2, which of the following could be a prime number?
a) w-12
b) w^4
c) w^2
d) w/4
e) 5w
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problem with prime numbers
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beatthegmatinsept
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One more for A. Agree with uwhusky, all other choices cant be prime numbers.
You could plug in numbers to test.
eg A. 17-12 = 5 (prime number)
You could plug in numbers to test.
eg A. 17-12 = 5 (prime number)
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Gurpinder
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I would go with (A).Taniuca wrote:what would be the easiest way to solve this type of problem?
If w is a prime number greater than 2, which of the following could be a prime number?
a) w-12
b) w^4
c) w^2
d) w/4
e) 5w
If W is a prime number greater than 2, means that its an odd number.
a) could be because lets say W is 17. so 17-12=5
b) doesn't work because the answer would be divisible by W
c) same reason as (b)
d) the number doesn't even have to be an integer.
e) the result of this one would be also divisible by 5 or the prime number.
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venmic
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the most imporatnt concept here os
prime* prime = non prime
5*5 = 25
7*7 = 49
prime - nonprime = prime
17-12 =5
prime + prime = nonprime
more than working with numbers
work with teh concept
prime* prime = non prime
5*5 = 25
7*7 = 49
prime - nonprime = prime
17-12 =5
prime + prime = nonprime
more than working with numbers
work with teh concept
venmic wrote:the most imporatnt concept here os
prime* prime = non prime
5*5 = 25
7*7 = 49
prime - nonprime = prime
17-12 =5
prime + prime = nonprime
more than working with numbers
work with teh concept
"prime - nonprime = prime" Is not always true, for example,
97 - 12 = 85 (non-prime).
It could be true for certain values of w.
The other answer options would always result in a non-prime number for all prime values of w.
Thus, w - 12 is the answer.
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GMATGuruNY
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Make a quick list of prime numbers greater than 2:Taniuca wrote:what would be the easiest way to solve this type of problem?
If w is a prime number greater than 2, which of the following could be a prime number?
a) w-12
b) w^4
c) w^2
d) w/4
e) 5w
w = {3, 5, 7, 11, 13, 17, 19, 23, 29...}
Answer choice A works when w=29:
w-12 = 29-12 = 17, which is prime.
The correct answer is A.
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Hi All,
Rather than CHOOSING A, we can eliminate all the others very easily.
1) w^4 and w^2 are divisible by w itself.
2) w/4, If w is a prime no, then w/4 will definitely be a fraction. So not a prime number .
3) 5w is divisible by 5.
All the other 4 options definitely will not give a prime number.
so has to yield any prime number.
Sid
Rather than CHOOSING A, we can eliminate all the others very easily.
1) w^4 and w^2 are divisible by w itself.
2) w/4, If w is a prime no, then w/4 will definitely be a fraction. So not a prime number .
3) 5w is divisible by 5.
All the other 4 options definitely will not give a prime number.
so has to yield any prime number.
Sid
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