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How many four digit integers do not contain any digits other

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CEO
Joined: 21 Jan 2007
Posts: 2734

Kudos [?]: 1085 [0], given: 4

Location: New York City
How many four digit integers do not contain any digits other [#permalink]

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15 Nov 2007, 07:50
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

How many four digit integers do not contain any digits other than 1 or 0 and are such that the sum of the first two digits equals the sum of the last two digits?

3
4
8
10
12

Kudos [?]: 1085 [0], given: 4

Director
Joined: 13 Dec 2006
Posts: 506

Kudos [?]: 253 [0], given: 0

Location: Indonesia

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15 Nov 2007, 07:53

1001, 1010, 1111

Amar

Kudos [?]: 253 [0], given: 0

Director
Joined: 30 Nov 2006
Posts: 590

Kudos [?]: 319 [0], given: 0

Location: Kuwait

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15 Nov 2007, 09:04
1111
1010
0101
1001
0110
0000

Total = 8

Kudos [?]: 319 [0], given: 0

SVP
Joined: 29 Aug 2007
Posts: 2470

Kudos [?]: 867 [0], given: 19

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15 Nov 2007, 12:11
Mishari wrote:
1111
1010
0101
1001
0110
0000

Total = 8

A. there are only 6, not 8, possibilities in your solutions and number/integers with 0 at the begaining are not considered 4 digit integers.

1001, 1010 and 1111 are the solutions.

Kudos [?]: 867 [0], given: 19

CEO
Joined: 21 Jan 2007
Posts: 2734

Kudos [?]: 1085 [0], given: 4

Location: New York City

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17 Nov 2007, 10:31
GMAT TIGER wrote:
Mishari wrote:
1111
1010
0101
1001
0110
0000

Total = 8

A. there are only 6, not 8, possibilities in your solutions and number/integers with 0 at the begaining are not considered 4 digit integers.

1001, 1010 and 1111 are the solutions.

0 cannot be the 1st digit in an integer.
OA is A

Kudos [?]: 1085 [0], given: 4

Director
Joined: 01 May 2007
Posts: 793

Kudos [?]: 390 [0], given: 0

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17 Nov 2007, 12:05
Concur 3. Integers cannot start with 0 and also 0000 is not a integer. All the #s must start with 1 in this case.

Kudos [?]: 390 [0], given: 0

Intern
Joined: 01 Nov 2007
Posts: 4

Kudos [?]: [0], given: 0

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17 Nov 2007, 13:16
yeah rgt...

when the first digitis fixed left is three places to be filled....hundreds..tens and units.....

..so for the two numbers 1 and 0...

if hundres is filled by 1...then units and tens both should have a 1.....so 1 way....

if hundreds is filled by zero....then units and tens either one can have 1 and the other zero....so two ways.....

so totally three ways.....

Kudos [?]: [0], given: 0

17 Nov 2007, 13:16
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How many four digit integers do not contain any digits other

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