How many four digit integers do not contain any digits other

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How many four digit integers do not contain any digits other [#permalink]

15 Nov 2007, 07:50

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

Please walk me thru the answer.

Director

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15 Nov 2007, 07:53

Answer 3

1001, 1010, 1111

Amar

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15 Nov 2007, 09:04

1111
1010
0101
1001
0110
0000

Total = 8

ANSWER: C

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15 Nov 2007, 12:11

Mishari wrote:

1111
1010
0101
1001
0110
0000

Total = 8

ANSWER: C

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.

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17 Nov 2007, 10:31

GMAT TIGER wrote:

Mishari wrote:

1111
1010
0101
1001
0110
0000

Total = 8

ANSWER: C

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

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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.

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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.....

[#permalink] 17 Nov 2007, 13:16

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How many four digit integers do not contain any digits other

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How many four digit integers do not contain any digits other

How many four digit integers do not contain any digits other

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