factors

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factors

by luckypiscian » Thu Jul 18, 2013 1:26 am
If x is the smallest positive integer that is not prime and not a factor of 50!, what is the sum of the factors of x?

51
54
72
162
50!+2

QA is D considering x as 53*2 = 106
why can't x be 52, i.e. non prime and not a factor of 50!

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by jitsy » Thu Jul 18, 2013 4:19 am
x cannot be 52 since 52 is 26*2 and since both both 2 and 26 are present in 50!, 52 is a factor of 50!

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by jitsy » Thu Jul 18, 2013 4:29 am
Good question though luckypiscian. Can I ask where this is from. Thank you.

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by luckypiscian » Thu Jul 18, 2013 4:34 am
OOPS ... my bad
this is from Veritas

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by jitsy » Thu Jul 18, 2013 4:49 am
Haha, np mate, happens!
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by vipulgoyal » Wed Jul 24, 2013 11:13 pm
the number is 51

1+3+17+51 = 72 ans

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by Matt@VeritasPrep » Thu Jul 25, 2013 9:19 am
Hey, I wrote this one! (Though it isn't an original idea :D)

Vipul, the answer isn't 51, as 51 is a factor of 50! (3 * 17 is part of 50!, so 50! divides by 51.)

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by vipulgoyal » Thu Jul 25, 2013 10:11 pm
my bad, no is 106, sum of factors are 1+2+53+106 = 162

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by jitsy » Thu Jul 25, 2013 10:50 pm
Good job Matt! Its a great question!
Matt@VeritasPrep wrote:Hey, I wrote this one! (Though it isn't an original idea :D)

Vipul, the answer isn't 51, as 51 is a factor of 50! (3 * 17 is part of 50!, so 50! divides by 51.)
If you appreciated my post or even just my time trying to help, please don't forget to click on 'Thanks' and say "Piece o' Cake mate" at the same time.