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by goyalsau » Sat Nov 27, 2010 3:59 am
Viper83 wrote:Is the positive integer x a multiple of 3 ?

(1) x is a multiple of 27.

(2) x is a multiple of 9.


does someone know how to do this?

Answer should be D,

I) For a number to be a multiple of 27 , It must have at least 3^3 when we factor it to prime numbers, So it must be multiple of 3 ,

II ) Same as first for a number to be a multiple of 9 , It should have at least 3 ^2 in its prime factor form,
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by frank1 » Sat Nov 27, 2010 5:52 am
Viper83 wrote:Is the positive integer x a multiple of 3 ?

(1) x is a multiple of 27.

(2) x is a multiple of 9.


does someone know how to do this?
answer to how
My approach would be
mind work every multiple of 27 should be multiple of 3
same for 9
take some value 27,54,108
45,54,90
way to check if it is divisible by 3 is
sum of number should be divisible by 3
ir 4+5=9
2+7=9

method 2:traditional one
x= 27 X some value
so 27 x some value /3 will be always integer until some value is integer as 27/3 will be always integer which means it will be always multiple
same for 9 ie 9/3 will always cancel

so should be D
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by Viper83 » Sat Nov 27, 2010 6:41 am
yes D is correct.
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