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daretodream: Senior | Next Rank: 100 Posts; Posts: 76; Joined: Tue Oct 28, 2008 6:08 am; Thanked: 2 times

by daretodream » Fri Feb 19, 2010 3:39 am

What is the value of integer J?

1. |J| = J^{-1}
2. J^J = 1

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Source: Beat The GMAT — Data Sufficiency | Fri Feb 19, 2010 3:39 am

ajith: Legendary Member; Posts: 1275; Joined: Thu Sep 21, 2006 11:13 pmFollowed by: 2 members; Location: Arabian Sea; Thanked: 125 times

by ajith » Fri Feb 19, 2010 4:46 am

daretodream wrote:What is the value of integer J?

1. |J| = J^{-1}
2. J^J = 1

1) |J| = J^{-1}

|J| is always +ve
J^{-1} should be +ve always
J is positive

j=1

Sufficient

2) J = +/- 1 ; insufficient

A

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thephoenix: Legendary Member; Posts: 1560; Joined: Tue Nov 17, 2009 2:38 amFollowed by: 5 members; Thanked: 137 times

by thephoenix » Fri Feb 19, 2010 10:04 am

daretodream wrote:What is the value of integer J?

1. |J| = J^{-1}
2. J^J = 1

s1)first statement says |J| = 1/J

the only value that is possible is1, so SUFF

s2)second statement

J^J = 1

J could be 0 or 1. 1^1 = 1 , 0^0=1

so INSUFF

hence A

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November Rain: Senior | Next Rank: 100 Posts; Posts: 50; Joined: Tue Oct 13, 2009 1:25 am; Thanked: 14 times; GMAT Score:720

by November Rain » Fri Feb 19, 2010 10:48 am

IMO B

1. can be either (-1/1 = -1) or (1/1 = 1)

2. only positive 1 can satisfy this equation, because 0^0 is undeffined and it can't be -1 because it has an odd exponent[/spoiler]

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shashank.ism: Legendary Member; Posts: 1022; Joined: Mon Jul 20, 2009 11:49 pmFollowed by: 2 members; Location: Gandhinagar; Thanked: 41 times

by shashank.ism » Sat Feb 20, 2010 1:53 pm

November Rain wrote:IMO B

1. can be either (-1/1 = -1) or (1/1 = 1)

2. only positive 1 can satisfy this equation, because 0^0 is undeffined and it can't be -1 because it has an odd exponent[/spoiler]

Yeah I am of the same view that 0^0 is indeterminate....

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girish3131: Master | Next Rank: 500 Posts; Posts: 194; Joined: Thu Jan 14, 2010 5:18 am; Thanked: 2 times

by girish3131 » Tue Mar 09, 2010 4:34 am

good ques...!

IMO D

wat's OA..

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outreach: Legendary Member; Posts: 748; Joined: Sun Jan 31, 2010 7:54 amFollowed by: 3 members; Thanked: 46 times

by outreach » Tue Mar 09, 2010 5:17 am

option 1
|J| = J^{-1}
=> J*|J|=1
J can only have one value that is 1. Hence suff

option 2
J^J = 1
=>j=+1 or -1
insufficient

OA is A

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schumi_gmat: Master | Next Rank: 500 Posts; Posts: 377; Joined: Wed Sep 03, 2008 9:30 amFollowed by: 2 members; Thanked: 15 times

by schumi_gmat » Tue Mar 09, 2010 9:58 pm

A is sufficient everbody agrees

B I was thinking that it was J raise to J and not sqr(J).

J^J = J^0 implies J=0.

when we resubstitute, 0^0 is indeterminate.

Hence A

Good Problem !!

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girish3131: Master | Next Rank: 500 Posts; Posts: 194; Joined: Thu Jan 14, 2010 5:18 am; Thanked: 2 times

by girish3131 » Tue Mar 09, 2010 10:51 pm

Mr outreach N Schumi

i know

J^J = J^0 implies J=0.

when we resubstitute, 0^0 is indeterminate.

AND

option 2
J^J = 1
=>j=+1 or -1
insufficient # wch is wrong ofcourse

BUT consider this thing

J^J = 1 ONLY TRUE In case of when J=1

when u put J=-1 then it become (-1)^(-1) IS NOT EQUAL TO 1 (BECAUSE THIS IS NOT LIKE (-1)(-1) )SO WE CAN NOT CONSIDER THIS SCENARIO EQUAL TO ONE...

HENCE ANS IS D

N outreach

wen u put yr ans then put IMO not OA....

ta

HENCE WE CAN SAY THAT

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raisethebar: Senior | Next Rank: 100 Posts; Posts: 55; Joined: Wed Dec 16, 2009 4:10 am

by raisethebar » Wed Mar 10, 2010 1:51 am

Agree with Ans D

J^J =1

For second statement concider 1 values for J=1 and J=-1
When J=1
1^1 =1

when J=-1
it will be (-1)^ -1 = 1/(-1) =-1 this is not true.

so we can conclude the 2nd statement itself is sufficient.

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ShakeM: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Thu May 21, 2009 9:57 pm

by ShakeM » Sun Mar 14, 2010 1:46 am

Agree with D.

To satisfy the 1st equation J can only be 1.

(-1)^(-1) is not abs(-1), hence -1 cannot be the integer.

To satisfy the second equation J can only be 1.

(-1)^(-1) does not satisfy the second equation.

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Phirozz: Master | Next Rank: 500 Posts; Posts: 232; Joined: Sun Feb 28, 2010 10:47 pm; Thanked: 10 times

by Phirozz » Sun Mar 14, 2010 7:45 am

daretodream wrote:What is the value of integer J?

1. |J| = J^{-1}
2. J^J = 1

IMO D. Both r independently sufficient
whats the OA ?

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