Q: find the sum of all common prime factors of 51 and 204

so I found 1, 3, 17 for the common prime factors of those two numbers. but does "1" count and a common prime factor?

my answer: 20 or 21??

thanks you

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- Mar 4th 2010, 06:18 PMpandakrapfind the prime factor of two numbers
Q: find the sum of all common prime factors of 51 and 204

so I found 1, 3, 17 for the common prime factors of those two numbers. but does "1" count and a common prime factor?

my answer: 20 or 21??

thanks you - Mar 4th 2010, 06:27 PMtonio

1 is not considered a prime number...and how come 20 or 21??? It is straightforward that neither divides 51...(Itwasntme)

We have $\displaystyle 51=3\cdot 17\,,\,\,204=2^2\cdot 3\cdot 17$ ....look carefully at these two prime factorings and now: what's the greatest common divisor of 51 and 204?

Tonio - Mar 5th 2010, 02:52 AMHallsofIvy
I think you misread the post, Tonio. The question was NOT "what is the greatest common factor". The question was "what is the

**sum**of the common prime factors. If the only common prime factors are 3 and 17 then the sum is 20. - Mar 5th 2010, 05:04 AMtonio

That "I misread the post" is an understatement: I must have been high, drunk or both when I dealt (?) with it. This is funny since I do no drugs at all and only drink alcoholic beverages once in a while, and also that in very minimal quantities.

I hope the OP didn't get too confused with my nonsense.

Tonio