|
Author |
Message |
|
TAGS:
|
|
|
Current Student
Joined: 28 Dec 2004
Posts: 3439
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 11
Kudos [?]:
134
[0], given: 2
|
Even Tougher Number Properties.... [#permalink]
 11 Oct 2005, 18:01
show working....
Attachments
 math-2.doc [54.5 KiB]
Downloaded 43 times
|
|
|
|
|
|
|
SVP
Joined: 24 Sep 2005
Posts: 1913
Followers: 7
Kudos [?]:
55
[0], given: 0
|
the product of first 8 positive integers is 1.2.......8 , this includes 2.4.8= 64 ---> (1) is ok.
(1) a^n= 64, there are several cases:
2^6, 4^3, 8^2 ----> (1) alone is insuff
(2) n=6 , say nothing
if (1) and (2) together, a^6=64---> a=2
C?
|
|
|
|
|
|
Director
Joined: 21 Aug 2005
Posts: 803
Followers: 2
Kudos [?]:
2
[0], given: 0
|
1.) Insuff.
can be 2^6 or 8^2 both 2 and 8 divide the product of 1st 8 numbers
2.) Insuff.
Together, we can say a=2 as n=6
So C
|
|
|
|
|
|
Senior Manager
Joined: 02 Oct 2005
Posts: 307
Followers: 1
Kudos [?]:
2
[0], given: 0
|
Product of first 8 numbers give 2^7 * 3 ^ 2 * 5 * 7
1. Has multiple choices
2. I ignored because it would take time to calc something power 6
So I concluded the answer to be C
Can we really ignore stmt 2 or we are ignoring just because of complex calculation (or) can it be proven that it has many possibilites?
|
|
|
|
|
|
Manager
Joined: 04 May 2005
Posts: 136
Location: Chicago
Followers: 1
Kudos [?]:
1
[0], given: 0
|
I get B. This is why.
1. insuff. a^n=64, a=n=8 or a=2 n=6
2. suff. Because we know that 8! is multiple of a^n means that 8! has to be evenly divided by a^n. If n=6 and we know that a>1, then we know that a=2 for 8! to be divisible by a^n. I broke it down like this:
8*7*6*5*4*3*2*1=b(a^6), where b is some multiple and it has to be an integer for it to be a multiple. If a=2, then 8! is evenly divided by 2^6, but any number above 2 will not work.
What is the OA and OE?
_________________
Christopher Wilson
|
|
|
|
|
|
SVP
Joined: 24 Sep 2005
Posts: 1913
Followers: 7
Kudos [?]:
55
[0], given: 0
|
chriswil2005 wrote: I get B. This is why.
1. insuff. a^n=64, a=n=8 or a=2 n=6
2. suff. Because we know that 8! is multiple of a^n means that 8! has to be evenly divided by a^n. If n=6 and we know that a>1, then we know that a=2 for 8! to be divisible by a^n. I broke it down like this:
8*7*6*5*4*3*2*1=b(a^6), where b is some multiple and it has to be an integer for it to be a multiple. If a=2, then 8! is evenly divided by 2^6, but any number above 2 will not work.
What is the OA and OE?
great job! I didn't see through this. Thank you!!
|
|
|
|
|
|
Current Student
Joined: 28 Dec 2004
Posts: 3439
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 11
Kudos [?]:
134
[0], given: 2
|
OA is B...
Chris if you can do this problem...you will score 48+ on the real exam...
|
|
|
|
|
|
Manager
Joined: 04 May 2005
Posts: 136
Location: Chicago
Followers: 1
Kudos [?]:
1
[0], given: 0
|
fresinha. Thanks for the encouragement. However, I have already taken that darn test (I vow to never say the name again) and I can't seem to get in the 40s. Practice tests, sure no problem, but the real test just makes me nervous. 
I take the test again in couple weeks.
_________________
Christopher Wilson
|
|
|
|
|
|
Senior Manager
Joined: 02 Oct 2005
Posts: 307
Followers: 1
Kudos [?]:
2
[0], given: 0
|
Thanks for the answer chriswil2005.
I had a small hunch that n=6, would give some clue, however I did not attack the problem in these lines.
My 2 cents: Be confident & do not get nervous, you would score high.
|
|
|
|
|
|
Current Student
Joined: 28 Dec 2004
Posts: 3439
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 11
Kudos [?]:
134
[0], given: 2
|
this time it will be different....
look I scored 49 Q on this CAT, and this was one of the hardest problems on it...so if you can do this...you are going to score high...trust me....
just dont loose your nerves....
chriswil2005 wrote: fresinha. Thanks for the encouragement. However, I have already taken that darn test (I vow to never say the name again) and I can't seem to get in the 40s. Practice tests, sure no problem, but the real test just makes me nervous. I take the test again in couple weeks. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
close
