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![[Post New]](/templates/default/images/icon_minipost_new.gif) 28 Jan 2008 21:23:20 IST
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actually i m cofused in d conclusion. how cn u arrange six boys n six girls in a row alternatively? my conclusion:- 1. by applying gap methode- 6! 7P6. bt some where d ans s 2 6! 6! moreover there are 2 ways of arranging 4 gals n 3 boys alternatively. i.e. 4! 3! and 4! 5P3 .....so s dis violating the rule???????
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28 Jan 2008 21:44:24 IST
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OOPS! SORRY ELASTIBOYSAI I POSTED THE WRONG ANSWER
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28 Jan 2008 21:59:04 IST
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gopal n viv, hey ur methods r wrong. coz by usin 7p6, u r includin cases where 1st gap is chosen, 2nd gap is missed n remaining gaps r chosen heres the correction. _g1_g2_g3_g4_g5_g6_ there are cases in wich girls are seated together in ur method. now subtract cases in wich girls are seated together. say fix a girl in pos1 now 5 girls can sit adjacent to her and remaining people can permute in 6!*6! times. so suybtract 5*6!*6! from da ans u got, i.e 7*6!*6! so ans is 2*6!*6! so ans gvn is correct nudge if doubtful, rate if useful
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28 Jan 2008 22:02:47 IST
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im no math genius ..but i agree wid elastiboysai..
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Nitwit Blubber Odment Tweak
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28 Jan 2008 22:07:29 IST
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SRY
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28 Jan 2008 22:33:36 IST
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well done elastic,nudge if useful rate if useless
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29 Jan 2008 00:30:26 IST
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hey but in the second part(ie. ways of arranging 4 gals n 3 boys alternatively.) 4! 5P3 is wrong according to the above concepts.
please help.
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30 Jan 2008 20:36:37 IST
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let me clear t. -g-g-g-g-g-g- . g for girls. so there r 7 gaps between those gals where u cn arrange the 6 boys in 7P6 ways. Now the gals cn b arranged by 6!. so total ways 6! 7P6. reference M.L. Khanna..
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30 Jan 2008 20:44:49 IST
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once if we arrange boys in a row _b1_b2_b3_b4_b5_b6_ whe have two sets of six gaps to arrange 6 girls so the no.of ways to arrange boys is 6! and girls is 6!x2 bcoz there are 2 sets there fore the answer is 2x6!x6!
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31 Jan 2008 10:48:36 IST
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HEY BUT SOMEONE PLEASE HELP ME WITH THE SECOND PART.
WHY SECOND PART HAS TWO ANSWERS
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31 Jan 2008 22:24:47 IST
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hello? Is anyone there?/
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1 Feb 2008 08:29:46 IST
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for second qs...
i think u can arrange gals first...
- G - G - G - G -
u can arrange gals in 4! ways (4 gals , 4 positions)
now 5 places are left....
arrange boys in that....
5P3 ways...
so ans is 4! * 5P3
or u can arrange boys first
- b - b - b -
3! ways of arranging boys.....
4 places and 4 gals...so u can arrange them in 4! ways
ans - 4! * 3!
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I always like to walk in rain as no one can see me crying there :(
frnds are like diamonds , if u hit them , they don't break but they slip frm ur hands
-----It is better to be hated for what you are than to be loved for what you are not.----
*****wen love and skill work together--expect a masterpiece*****
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1 Feb 2008 08:33:00 IST
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ans i think ur 1st answer is correct...
m getting 6! * 7P6 too....
and my book also says the same thing....
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I always like to walk in rain as no one can see me crying there :(
frnds are like diamonds , if u hit them , they don't break but they slip frm ur hands
-----It is better to be hated for what you are than to be loved for what you are not.----
*****wen love and skill work together--expect a masterpiece*****
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1 Feb 2008 14:10:44 IST
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the concept of 'elasti' was right-
_g1_g2_g3_g4_g4_g5_g6
simply the girls can permutate among themselves in 6! ways and the boys in 7P6 ways.hence the answer - 6!*7p6.
what the serious glitch in the above method
is that we are not sure that the girls will sit continuosly
for eg one of the cases are
b1 g1 g2 b2 g3 b3 g4 b4 g5 b5 g6 b6
as we see that that the condition required in the question is not satisfied here .hence the general method is wrong anyways the general method is used in such examples->
find the ways of arranging 3 plus signs and 3minus in such a way that no two minus signs are together.(ans-3!*4p3)
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