GMATClub Diagnosis Questions wrong?

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sunman: Master | Next Rank: 500 Posts; Posts: 165; Joined: Thu Feb 17, 2011 5:05 amFollowed by: 9 members; Location: San Diego, CA; Thanked: 14 times; GMAT Score:750

by sunman » Wed Dec 28, 2011 6:42 pm

Alright, so this is getting really frustrating.

The answer key says that #1 could be 1, 2, 3, 4, or 0.

How can #1 be 0!, since 0! IS divisible by 5???? This is driving me up a wall. Is there something I'm missing, or are these questions just busted up?

Edit: The question is supposed to say: Is N divisible by 5?

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Source: Beat The GMAT — Data Sufficiency | Wed Dec 28, 2011 6:42 pm

pemdas: Legendary Member; Posts: 1084; Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members; Thanked: 158 times

by pemdas » Wed Dec 28, 2011 7:14 pm

factorial of 0 is 1 not 0

sunman wrote:Alright, so this is getting really frustrating.

The answer key says that #1 could be 1, 2, 3, 4, or 0.

How can #1 be 0!, since 0! IS divisible by 5???? This is driving me up a wall. Is there something I'm missing, or are these questions just busted up?

Edit: The question is supposed to say: Is N divisible by 5?

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sunman: Master | Next Rank: 500 Posts; Posts: 165; Joined: Thu Feb 17, 2011 5:05 amFollowed by: 9 members; Location: San Diego, CA; Thanked: 14 times; GMAT Score:750

by sunman » Wed Dec 28, 2011 7:17 pm

pemdas wrote:factorial of 0 is 1 not 0
sunman wrote:Alright, so this is getting really frustrating.

The answer key says that #1 could be 1, 2, 3, 4, or 0.

How can #1 be 0!, since 0! IS divisible by 5???? This is driving me up a wall. Is there something I'm missing, or are these questions just busted up?

Edit: The question is supposed to say: Is N divisible by 5?

Grrr....ok, how does that work? I've never dealt with 0 factorial before.

3! = 3x2x1
2! = 2x1
1! = 1x1?
0! = 0x1?

I don't get it.

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pemdas: Legendary Member; Posts: 1084; Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members; Thanked: 158 times

by pemdas » Wed Dec 28, 2011 7:20 pm

brrrrrr
1!=1
0!=1

they are not asking if N! is divisible by 5, rather N or 0

N! isn't divisible by 5 in st(1) implies N can be 0,1,2,3,4 and among these N=0 is divisible by 5

st(2) implies two numbers in unit's digit 0 and 9

combined two st-s imply only 0 and answer Yes, divisible Suff

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sunman: Master | Next Rank: 500 Posts; Posts: 165; Joined: Thu Feb 17, 2011 5:05 amFollowed by: 9 members; Location: San Diego, CA; Thanked: 14 times; GMAT Score:750

by sunman » Wed Dec 28, 2011 8:18 pm

pemdas wrote:brrrrrr
1!=1
0!=1

they are not asking if N! is divisible by 5, rather N or 0

N! isn't divisible by 5 in st(1) implies N can be 0,1,2,3,4 and among these N=0 is divisible by 5

st(2) implies two numbers in unit's digit 0 and 9

combined two st-s imply only 0 and answer Yes, divisible Suff

That's a garbage question that won't even be in the real GMAT.

Thank you though, I appreciate your expertise.

I still don't get the concept of "0 factorial". I doubt the GMAT would test on something so nebulous. This is my 3rd shot at the GMAT.

"Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it's the only thing that ever has" - Margaret Mead

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neelgandham: Community Manager; Posts: 1060; Joined: Fri May 13, 2011 6:46 amFollowed by: 52 members; Location: Utrecht, The Netherlands; Thanked: 318 times

by neelgandham » Thu Dec 29, 2011 3:56 am

sunman : See if this -> https://www.adonald.btinternet.co.uk/Factor/Zero.html and this https://www.zero-factorial.com/whatis.html answer your question

Anil Gandham
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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Thu Dec 29, 2011 8:29 am

sunman wrote: I doubt the GMAT would test on something so nebulous.

I agree that it's unlikely that you'd be tested directly on your knowledge of whether or not 0!=1.
However, you are tested on this indirectly when you use certain counting formulas.

For example, 3C3=3!/[(3!)(0!)]
Here, we need to know that 0!=1

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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sunman: Master | Next Rank: 500 Posts; Posts: 165; Joined: Thu Feb 17, 2011 5:05 amFollowed by: 9 members; Location: San Diego, CA; Thanked: 14 times; GMAT Score:750

by sunman » Thu Dec 29, 2011 9:28 am

Thanks guys, you're the best.

0!, what a stupid concept...haha

I swear to you, once I get that 49+ on quant, I'm never touching bloody freaking mathematics again. I got through my entire undergrad career without taking a single math class.

Alright...so my first try I got a 6/46/40 for a 700, 2nd try I had a disappointingly modest improvement at 6/47/41 for 710.

What does a similiarly modest improvement of 6/48/42 come out to?

800score's GMAT calculator says 750, but I think it's formula may be dubious.

Best case scenario I can pull a 49+ on quant and 42+ on verbal for something near a 750...but we'll see. Traditionally struggle on quant, and usually run dry on time. Even on the MGMAT tests, I rarely ever broke 48.

"Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it's the only thing that ever has" - Margaret Mead

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Thu Dec 29, 2011 9:39 am

sunman wrote:What does a similiarly modest improvement of 6/48/42 come out to?
800score's GMAT calculator says 750, but I think it's formula may be dubious.

750 seems a bit high.

This post suggests that 48Q + 42V = 730: https://www.beatthegmat.com/done-730-48q-42v-t42464.html

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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sunman: Master | Next Rank: 500 Posts; Posts: 165; Joined: Thu Feb 17, 2011 5:05 amFollowed by: 9 members; Location: San Diego, CA; Thanked: 14 times; GMAT Score:750

by sunman » Thu Dec 29, 2011 9:52 am

Brent@GMATPrepNow wrote:
sunman wrote:What does a similiarly modest improvement of 6/48/42 come out to?
800score's GMAT calculator says 750, but I think it's formula may be dubious.
750 seems a bit high.

This post suggests that 48Q + 42V = 730: https://www.beatthegmat.com/done-730-48q-42v-t42464.html

Cheers,
Brent

Ugh...if I could only keep my GMATPrep1 performance of 50/45 (770)

"Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it's the only thing that ever has" - Margaret Mead

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Thu Dec 29, 2011 9:56 am

sunman wrote:Ugh...if I could only keep my GMATPrep1 performance of 50/45 (770)

If you did it once, you can do it again!!

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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neelgandham: Community Manager; Posts: 1060; Joined: Fri May 13, 2011 6:46 amFollowed by: 52 members; Location: Utrecht, The Netherlands; Thanked: 318 times

by neelgandham » Thu Dec 29, 2011 11:50 am

sunman wrote: What does a similiarly modest improvement of 6/48/42 come out to?

Q48 V42 - 730
Q49 V42 - 740/750
Q50 V42 - 750/760
Q50 V43 - 760
Q51 V42 - 760/770

Source: Previous scores. Hope it helps !

Anil Gandham
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[email protected]: Legendary Member; Posts: 934; Joined: Tue Nov 09, 2010 5:16 amFollowed by: 14 members; Location: AAMCHI MUMBAI LOCAL; Thanked: 63 times

by [email protected] » Sat Jan 21, 2012 10:14 pm

I completely understood the question but I did not get this point:

how is 0 divisible by 9

from that perspective, 0 is divisible by every number....

I also got the first statement of this question!!!

Can anyone plss help...

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