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Source: — Data Sufficiency |
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by kul512 » Thu Feb 23, 2012 7:51 am
I must say that collection of DS problems is very nice.
Hareesh this is your first question-
1) How many different prime numbers are factors of the positive integer n ?
(1) Four different prime numbers are factors of 2n.
(2) Four different prime numbers are factors of n2.

Statement1:
2n has four different prime factors.
two possibilities are there-
n already has four different prime factors and 2 is one of the factors, to say- n=2X3X5X7 so now 2n will also have only 4 different prime factors.
n has only three prime factors i.e. n=3X5X7. After multiplying with 2 we will get total 4 different prime factors.
So this information is not sufficient.

Statement2:
n2 has four different prime factors.
TO BE REMEMBERED: DIFFERENT PRIME FACTORS OF ANY POWER OF A NATURAL NUMBER WILL ALWAYS BE SAME AS THE DIFFERENT PRIME FACTORS OF THE ORIGINAL NUMBER.
so if n2 is having four different prime factors, n will also be having 4 different prime factors.
Sufficient

Answer (B)
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by Mike@Magoosh » Mon Feb 27, 2012 3:15 pm
Hi, there, I'm happy to help here.

First of all, I've posted a complete solution to all the questions in the attached pdf.

Also, if you are just getting started understanding DS, here's a blog and free video that you may fine helpful.

https://magoosh.com/gmat/2012/introducti ... fficiency/

Let me know if you have any questions.

Mike :)
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14 DS questions, with solutions.pdf
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Magoosh GMAT Instructor
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