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#1 2006-11-20 05:27:25
- RauLiTo
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- From: Bahrain
- Registered: 2006-01-11
- Posts: 142
whats the remain
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$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...
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#2 2006-11-20 06:45:40
- pi man
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- Registered: 2006-07-06
- Posts: 251
Re: whats the remain
Let X be the first number with a remainder of 3. So X = 7a + 3
Let Y be the second number with a remainder of 5. So Y = 7b + 5
XY = (7a+3) * (7b+5)
= 49ab + 35a + 21b + 15
49ab, 35a, and 21b are all divisible by 7. We only need to worry about the 15, which is 2*7 with a remainder of 1.
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#3 2006-11-20 08:08:19
- RauLiTo
- Member
- From: Bahrain
- Registered: 2006-01-11
- Posts: 142
Re: whats the remain
lol thats easy ! thanks pi
ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...
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