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#1 2015-10-18 19:00:33

Divine
Member
Registered: 2015-10-18
Posts: 5

Basic Operation

Question:

From four numbers, how many 4-digit codes can be made if no number is repeated in a code?

Please answer it with explanation or solutions. thank you..

Last edited by Divine (2015-10-18 19:14:21)

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#2 2015-10-18 19:13:46

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Basic Operation

What 4 numbers? 0 - 9? Can the first digit be a zero?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#3 2015-10-18 19:18:24

Divine
Member
Registered: 2015-10-18
Posts: 5

Re: Basic Operation

i dont know but these are the choices from the questionnaire,  12, 14, 18, 20 & 24.

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#4 2015-10-18 19:21:28

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Basic Operation

Then choose 24.

4 x 3 x 2 x 1


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#5 2015-10-18 19:34:13

Divine
Member
Registered: 2015-10-18
Posts: 5

Re: Basic Operation

thank you bobby.. i guess it is 24..

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#6 2015-10-18 19:36:48

Divine
Member
Registered: 2015-10-18
Posts: 5

Re: Basic Operation

Bobby can u answer this? IF (A+B) IS THE COMMON FACTOR OF X(A+B)-(A+B), WHAT IS THE OTHER FACTOR?

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#7 2015-10-18 19:44:21

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Basic Operation

You can factor that into:

Do you see the other factor?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#8 2015-10-18 20:41:59

Divine
Member
Registered: 2015-10-18
Posts: 5

Re: Basic Operation

i don't know. but these are the choices
1. x
2. x(x-b)
3. x-1
4. x(a+b)
5. x+1
my co worker answer is (a+b)squared.

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#9 2015-10-18 22:06:01

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Basic Operation

I would go with 3) x - 1


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#10 2015-10-19 04:27:46

zetafunc
Moderator
Registered: 2014-05-21
Posts: 2,432
Website

Re: Basic Operation

Divine wrote:

thank you bobby.. i guess it is 24..

How many choices do you have for the first number?

Now that the first choice is set, you can't pick that number again. So how many choices do you have for the second number? Then the third, and fourth?

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