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an=a1+d(n-1)

a18=a1+2(18-1)=24

the first positive number in this set is 2

24-2=22

by LalaB

Tue Nov 20, 2012 9:47 pm
Forum: Problem Solving
Topic: Set
Replies: 3
Views: 1286

I am not a wife,but I already posted the rule for divisibility by 11 :)

the quickest method is to guess and move on (kidding!)

Brent, I liked ur post. This shows again that most of the gmat questions can be solved in multiple ways. that is why we love (do we!? I am a liar hehe) the gmat )))

by LalaB

Thu Oct 18, 2012 10:07 am
Forum: Problem Solving
Topic: divisible by 11
Replies: 8
Views: 4284

answer choice C says n minus 100 ; 14444-100=14344 it is divisible by 11 (check it by summing up digits in odd places,then digits in even places. if the sum of digits in odd places is equal to the sum of digits in even places, then the number is divisible by 11) 1+3+4=4+4 so, 14544 is divisible by 1...

by LalaB

Wed Oct 17, 2012 9:35 pm
Forum: Problem Solving
Topic: divisible by 11
Replies: 8
Views: 4284

one more solution-

average= (last term+first term)/2=(A160th+A1)/2

note that we have the following set-
6 9 12 15 etc

it means we have multiple of 3 plus 3 . a1=1*3+3=6 a2=2*3+3=9 etc

so, A160=160*3+3=483

(483+6)/2=244.5

by LalaB

Thu Oct 04, 2012 7:56 am
Forum: Problem Solving
Topic: Average | Manhattan strategy guides
Replies: 9
Views: 2762

let the radius of a circle be x since the triangle is equilateral, its angle is equal to 60degree the bottom of the triangle is 2x, the diagonal is x*sqroot3 the area of the triangle =2x*x*sqroot3/2=(x^2)*sqroot3 the area of the sector of a cirle =(60/360)*pi*x^2=(1/6)*pi*x^2 so we have - (x^2)*sqro...

by LalaB

Mon Oct 01, 2012 11:56 pm
Forum: Problem Solving
Topic: 3 Tangent circles
Replies: 2
Views: 6795

Well now I get a ans , can someone clarrify what Im doing wrong here. Using slot method. 1st slot : select 1 women from 8 ppl out of 5 women = 5/8 2nd slot : selecting 2nd women = 4/7 3rd slot : selecting 1 man from remaining ppl out of 3 men = 3/6 4th slot : selecting 2nd man = 2/5 5/8*4/7*3/6*2/5...

by LalaB

Mon Oct 01, 2012 11:24 pm
Forum: Problem Solving
Topic: A small company employs 3 men and 5 women. If a team of 4 em
Replies: 12
Views: 14044

four married couples=4*2= 8 people

we need to get 6 ppl(excluding 2 married) out of 8
8!/6!/2!=32

by LalaB

Mon Oct 01, 2012 8:58 am
Forum: Problem Solving
Topic: permutation
Replies: 7
Views: 5334
by LalaB

Mon Oct 01, 2012 8:41 am
Forum: Problem Solving
Topic: Probability/ combination
Replies: 6
Views: 3025
by LalaB

Mon Oct 01, 2012 8:33 am
Forum: Problem Solving
Topic: Mechanics Question
Replies: 25
Views: 12176
by LalaB

Mon Oct 01, 2012 1:53 am
Forum: Problem Solving
Topic: Probability - balls - need expert help
Replies: 6
Views: 1616

1)
4^(x+1)-4^(x-1)>100

4^(x+1)-4^x/4>100

(4^x)*4*4-4^x>400
4^x(16-1)>400
(4^x)*15> 400
26<4^x<100

x=3

2) 4^(x + 1) + 4^x > 100

4^x(4+1)>100
4^x>20

20<4^x<100
x=3
ans is D

by LalaB

Thu Sep 27, 2012 7:40 am
Forum: Data Sufficiency
Topic: confused with this DS
Replies: 6
Views: 1512

can you please keep track of my questions , Am suffering a lot lately due to combinations, would really appreciate your help ( have also asked @kanwar for his assistance). I have found quite a few combinotrics questions whose solutions I am not sure about, Hope I will be able to find help in this c...

by LalaB

Thu Sep 06, 2012 6:53 am
Forum: Problem Solving
Topic: Nine dogs are split into 3 groups to pull one of three sled
Replies: 8
Views: 1966

gmatter2012 wrote:Thank you LalaB, these formula's, Good to know.
u r welcome. glad to be helpful, and good luck with ur study

by LalaB

Thu Sep 06, 2012 6:44 am
Forum: Problem Solving
Topic: Nine dogs are split into 3 groups to pull one of three sled
Replies: 8
Views: 1966

well, yes, in this case order is important. Remember- if u want to get m groups, each containing n objects, and order matters, then use the formula - (mn)!/(n!)^m so, in this case we have (3*3)!/(3!)^3 if u want to get m groups, each containing n objects, and order doesnt matter, then use the formul...

by LalaB

Thu Sep 06, 2012 12:49 am
Forum: Problem Solving
Topic: Nine dogs are split into 3 groups to pull one of three sled
Replies: 8
Views: 1966

see the reference- the title of this topic is Ä°an pliz! but the post is "Ä° need an ans!" and this sign (!) is scary :) Ian, if u dont answer within next 24 hours, I feel u will be sued for not answering :) we ,females, always need men to answer to our questions, such as- when did u come ...

by LalaB

Wed Sep 05, 2012 10:38 am
Forum: Lounge
Topic: Ian...plz rply!
Replies: 11
Views: 2562