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The number of numbers that can be formed by the digits 1,2,3,4,3,2,1. the odd digits are at odd places is given by
A) 430
B) 215
C) 93
D) 36
E) 18
Written by Chandu on June 18th, 2008 with
15 comments.
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The number of numbers that can be formed by the digits 1,2,3,4,3,2,1. the odd digits are at odd places is given by
A) 430
B) 215
C) 93
D) 36
E) 18
GRE Question of the Day by Chandu on June 18th, 2008 with
15 answers.
Read more articles on and and .
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Read the answer left by other GRE Takers below, or:
yadav
#2.
March 30th, 2007, at 4:53 PM.
madhur rocks!!!!
arun
#3.
April 2nd, 2007, at 10:14 AM.
4!/(2*2)x(3!/2)=18 ways.
isha
#4.
May 11th, 2008, at 1:40 AM.
hey guys…u rock!!!
how do u guys solve such ques.
Can somebuddy clear lil fundamental…so dat i can do gud in suchques…
Abhijeet
#5.
May 12th, 2008, at 4:54 PM.
Hi madhur , dont you think we should use permutation here as its arrangemnts not the selection. order of digits do have importance here.
From your updates :
4 odd numbers (1,1,3,3,) can be placed in 4 positions(1,3,5,7)
using 4!/(2!*2!) =6
you have used combination formula here.
I think the answer is 36. Let me know your comments.
nick
#7.
May 16th, 2008, at 6:03 AM.
The correct answerIS 18. The combination formula is the correct one to use- It does not matter, for example, which 3 or 1 is taking up an odd spot, so long as ONE of them is.
To solve this as a permutation would be double counting. A 3 is a 3… a 1 is a 1… a 2 is a 2…
Joel
#8.
May 25th, 2008, at 1:51 PM.
no of odds = 4, no of evens = 3. we have 7 slots arranged as: o e o e o e o
4 x 3 x 2 x 1 (for the odds) x 3 x 2 x 1 (for the evens)
—————————————————————–
2 x 2 x 2 (because 1,2,3 are repeated)
viki
#9.
June 18th, 2008, at 10:34 PM.
B
Anoop
#10.
June 19th, 2008, at 12:12 PM.
Guys.. Wht mathur did is rite..
See the question asks hw many numbers can be formed and that fact is inherent that duplicate numbers are be avoided. So Combination works out well here.
The answer is 18
sam
#11.
June 19th, 2008, at 4:06 PM.
E
pavithra
#12.
June 20th, 2008, at 4:11 AM.
ya its 18 i.e E
harini
#13.
June 22nd, 2008, at 9:30 PM.
ans is E: NO OF ODD NO’S 4!/2!*2!=6 ways whereas even nos 3!/2!=3ways total no of ways=6*3=18 ways.
sri
#14.
June 25th, 2008, at 10:00 PM.
A man spends a certain amount on rice every month. When price drops by Rs. 4 /kg, he is able to buy 16 kg more. When price increases by Rs. 9 /kg, he is able to buy 18 kg less.
col:A => Rate of rice
col:B => (1/51) *Expenditure on rice every month.
satish
#15.
July 26th, 2008, at 8:48 PM.
c is the answer
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Rama
#1. March 30th, 2007, at 3:30 PM.
E
4 odd numbers (1,1,3,3,) can be placed in 4 positions(1,3,5,7)
using 4!/(2!*2!) =6
Rest 3 even numbers (2,2,4) can be positioned in remaining 3 places
using 3!/2!=3
Answer = 6*3=18