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**RauLiTo****Member**- From: Bahrain
- Registered: 2006-01-11
- Posts: 142

a number divided by 7 and the remain is = 3 ... and another number divided by 7 also and the remain is = 5 ... whats the remain when we divide the product of these two numbers by 7 ?

*Last edited by RauLiTo (2006-11-20 05:33:38)*

ImPo$$!BLe = NoTH!nG

Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...

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**pi man****Member**- Registered: 2006-07-06
- Posts: 251

Let X be the first number with a remainder of 3. So X = 7a + 3

Let Y be the second number with a remainder of 5. So Y = 7b + 5

XY = (7a+3) * (7b+5)

= 49ab + 35a + 21b + 15

49ab, 35a, and 21b are all divisible by 7. We only need to worry about the 15, which is 2*7 with a remainder of 1.

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**RauLiTo****Member**- From: Bahrain
- Registered: 2006-01-11
- Posts: 142

lol thats easy ! thanks pi

ImPo$$!BLe = NoTH!nG

Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...

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