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Junior | Next Rank: 30 Posts
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prime factors ...

by Khaim » Thu Jul 16, 2009 4:00 pm
What is the sum of the different positive prime factors of 550 ?

A 10
B 11
C 15
D 16
E 18

I have no idea when trying to understand the question .....

Thanks
..Qui ne tente rien n'a rien
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by shibal » Thu Jul 16, 2009 4:04 pm
IMO 18 it's asking for the sum of the DIFFERENT prime factors of 550. brake it down into factor 5*5*2*11. the only DIFFERENT ones are 5,2,11. add them up to get 18.
hope it helps...
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Junior | Next Rank: 30 Posts
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by Khaim » Thu Jul 16, 2009 4:15 pm
I got it !!

I think I confuse with prime numbers ..... ( 2 is not a prime number and I was confused )

Thanks again
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by tim0thy » Fri Jul 17, 2009 8:51 am
Just to clarify, 2 IS a prime number. It is the first and only even prime number.

2+5+11 = 18 as Shibal outlined above[/quote]
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by ghacker » Fri Jul 17, 2009 9:39 am
550 = 55X10 or 25*22

so sum of factors = 5+11+2 =18
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