A computer password consists of two letters, which are

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A computer password consists of two letters, which are [#permalink]

08 Feb 2005, 23:02

A computer password consists of two letters, which are allowed to be repeated, and three numerical digits. how many passwords can be created?

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08 Feb 2005, 23:08

is it 71280.
That is if the number cannot be repeated but the two letters can be repeated

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08 Feb 2005, 23:15

26*26*10*10*10 if numbers can be repeated
26*26*10*9*8 otherwise.

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09 Feb 2005, 07:04

HONGHU'S ANSWER IS PERFECT. I AGREE WITH HI ANSWER.

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09 Feb 2005, 10:11

5C3 (10x9x8) *(26*26) = 10 (720)(676) = 4867200 ways..........assuming numbers can't be repeated.

Ques doesn't say that the password should have first 2 as letters and last 3 as numbers, they can be anywhere thus I think we need to multiply by 5C3 = 10 also.

Last edited by banerjeea_98 on 09 Feb 2005, 12:08, edited 1 time in total.

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09 Feb 2005, 11:45

Even I agree with Honghu' s answer

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09 Feb 2005, 12:28

banerjeea_98 wrote:

Great point!!!

I'd have said P(5,5)/(P(2,2)P(3,3)) though, what's your reasoning for C(5,3)? I mean we'd get the same number but obviously your method is better.

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09 Feb 2005, 12:30

Pick the positions for the numbers, and then put the letters into the remaining postions. I got you.

Or you can say C(5,2), same thing.

Good job baner!

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09 Feb 2005, 12:39

HongHu wrote:

Pick the positions for the numbers, and then put the letters into the remaining postions. I got you.

Or you can say C(5,2), same thing.

Good job baner!

Yep u got it, pick 3 positions or 2 positions, same ans. This is a combination, permutation problem.

[#permalink] 09 Feb 2005, 12:39

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A computer password consists of two letters, which are

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A computer password consists of two letters, which are

A computer password consists of two letters, which are

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