It is currently 28 Jun 2017, 03:32

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# why this is wrong?

Author Message
Current Student
Joined: 11 May 2008
Posts: 556

### Show Tags

29 Aug 2008, 10:40
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

where did i go wrong???
Attachments

test 2.doc [66 KiB]

SVP
Joined: 07 Nov 2007
Posts: 1799
Location: New York
Re: why this is wrong? [#permalink]

### Show Tags

29 Aug 2008, 10:51
arjtryarjtry wrote:
where did i go wrong???

_________________

Smiling wins more friends than frowning

Current Student
Joined: 11 May 2008
Posts: 556
Re: why this is wrong? [#permalink]

### Show Tags

29 Aug 2008, 11:02
pls guide me how to do so ,
Director
Joined: 12 Jul 2008
Posts: 515
Schools: Wharton
Re: why this is wrong? [#permalink]

### Show Tags

29 Aug 2008, 11:03
arjtryarjtry wrote:
where did i go wrong???

A. Tough one.

(1) Sufficient
t = 7k+6, where k is an integer

(7k+6)^2 + 5(7k+6) + 6
= 49k^2 +84k + 36 + 35k + 30 + 6
= 49k^2 + 119k + 72

49k^2 is divisible by 7.
119k is divisible by 7.
Thus, remainder is always remainder of 72/7, or 2.

(2) Insufficient

t^2 = 7k+1
t = +/-sqrt(7k+1) = an integer
t could be 6, 9, 15 etc...

If t = 6
t^2 + 5t + 6 = 36 + 30 + 6 = 72
72/7 = 10 R 2

If t = 15
t^2 + 5t + 6 = 225 + 75 + 6 = 306
306/9 = 34

Last edited by zonk on 29 Aug 2008, 11:41, edited 3 times in total.
SVP
Joined: 07 Nov 2007
Posts: 1799
Location: New York
Re: why this is wrong? [#permalink]

### Show Tags

29 Aug 2008, 11:04
arjtryarjtry wrote:
where did i go wrong???

1)
t= 7k+6

t^2+5t+6= 49k^2+2*7k*6+36+6
=49k^2+2*7k*6+72
divide this by 7 remainder always 2
suffcient
2)
t^2=7m+1

t^2+5t+6= 7m+1 +5t+6= 7m+7+ 5*t

m=9 t=8 5t = 40 REMAINDER 5
m=32 t=15 5t = 120 REMAINDER 1

not suffcient

A
_________________

Smiling wins more friends than frowning

Re: why this is wrong?   [#permalink] 29 Aug 2008, 11:04
Display posts from previous: Sort by