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If F is a factor of 105, is F is a prime number?
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25 Jul 2018, 04:02
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Re: If F is a factor of 105, is F is a prime number?
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25 Jul 2018, 04:07
If F is a factor of 105, is F is a prime number? 105=3*5*7.... Number of factors =2*2*2=8 Factors are 1,3,5,7,15,21,35,105 (1) F is not divisible by 3 So F can be 1,5,7,35... If 5 or 7, yes If 1 or 35, no Insufficient (2) F < 10 1,3,5,7.. If 3,5,7, yes If 1, no Insufficient Combined If 5 or 7, yes If 1, no Insufficient E
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Re: If F is a factor of 105, is F is a prime number?
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25 Jul 2018, 04:11
If F is a factor of 105, is F is a prime number?
(1) F is not divisible by 3
(2) F < 10
factors of 105: 1, 3, 5, 7, 15, 21, 35, 105
(1) F is not divisible by 3  Insufficient
F = 5 (prime) F = 35 (not prime)
(2) F < 10  Insufficient
F = 5 (prime) F = 1 (not prime)
(1)+(2)  Insufficient
F = 5 (prime) F = 1 (not prime)
Option E



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Re: If F is a factor of 105, is F is a prime number?
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25 Jul 2018, 06:41
Bunuel wrote: If F is a factor of 105, is F is a prime number?
(1) F is not divisible by 3
(2) F < 10 Note: F is a factor of 105. It means F mustn't be a prime factor. We are asked whether F is prime. Before Dealing with statement , it's better to factorize 105. 1*105 = 105 15*7 = 105 35*3 = 105 21*5 = 105 All these probable factors are listed above. Statement 1: F is not divisible by 3. Among the factors , 7 ,5 and 35 are not divisible by 3. 7 and 5 are prime but 35 and 1 are not. NOT sufficient. Statement 2: F < 10 . Still 1 , 7 , 5 are not divisible by 3. Where 7 and 5 are prime 1 is not. Not Sufficient. Combining both Statement : Still Not sufficient. The best answer is E.



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Re: If F is a factor of 105, is F is a prime number?
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07 Sep 2018, 07:29
Bunuel wrote: If F is a factor of 105, is F is a prime number?
(1) F is not divisible by 3
(2) F < 10
\(\frac{{3 \cdot 5 \cdot 7}}{F} = \operatorname{int}\) \(F\,\mathop = \limits^? \,\,{\text{prime}}\) \(\left( {1 + 2} \right)\,\,\,\left\{ \begin{gathered} \,F = 1\,\,\,\, \Rightarrow \,\,\,\left\langle {{\text{NO}}} \right\rangle \hfill \\ F = \,\,5\,\,\,\, \Rightarrow \,\,\,\left\langle {{\text{YES}}} \right\rangle \hfill \\ \end{gathered} \right.\) This solution follows the notations and rationale taught in the GMATH method. Regards, fskilnik.
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Re: If F is a factor of 105, is F is a prime number? &nbs
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