Hi all,

Got stuck with the following questions...need your help guys

Q1: Is "m" a multiple of 6?
1) More than 2 of the first 5 positive integer multiples of m are multiples of 3

2) Fewer than 2 of the first 5 positive integer multiples of m are multiples of 12

Couldn't get this one.....how should i go about such questions?


Q2: What is the sum of positive integers x and y?
1) x^2 + 2xy + y^2 = 16
2) x^2 - y^2 = 8

I got it D but dont know how number 2 statement can be proved...can anybody explain?

Q3: If x is an integer, is x even?
1) x^2 - y^2 = 0
2) x^2 + y^2 = 18

usman

Q1: Is "m" a multiple of 6?
1) More than 2 of the first 5 positive integer multiples of m are multiples of 3

2) Fewer than 2 of the first 5 positive integer multiples of m are multiples of 12

Plugging in numbers should give it to you.
1) If more than 2 of the first 5 positive integer multiples of m are multiples of 3, then the number itself must be a multiple of 3. However, this does not mean it is a multiple of 6. Insufficient.
e.g. m = 9, then first 5 integer multiples are 9, 18, 27, 36, 45.
or m = 6, then we have 6, 12, 18, 24, 30. Both satisfy the criteria, but 9 is not a multiple of 6.

2) If you take m=6, then 2 of the first 5 integer multiples are multiples of 12. Not so if you take any other number. Sufficient.

Hence B.

Q2: What is the sum of positive integers x and y?
1) x^2 + 2xy + y^2 = 16
2) x^2 - y^2 = 8

Exactly as Fig has explained.

Q3: If x is an integer, is x even?
1) x^2 - y^2 = 0
2) x^2 + y^2 = 18

Also exactly as Fig has explained.

I think (2) is 'D'

if X & Y are +ve integers(given), why should we consider x+y = -4 ?

//Yezz'z reply from the other post

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Q1: Is "m" a multiple of 6?
1) More than 2 of the first 5 positive integer multiples of m are multiples of 3

2) Fewer than 2 of the first 5 positive integer multiples of m are multiples of 12


M to be a multiple of 6 it takes the form = 3*2*k where k is positive intiger

from one

first five multiples are M ,m*2 , M*3 , m*4 , m*5

worst case scenario m*5,m*3,m are multiples of 3 , and m is thus a multiple of three but we need a factor of 2 at least to make sure m is multiple of 6........insuff

from 2

clearly insuff

both together still insuff

my answer is E



Q2: What is the sum of positive integers x and y?
1) x^2 + 2xy + y^2 = 16
2) x^2 - y^2 = 8
from one

(x+y)^2 = +or -ve sqrt 16 ie (x+y) might be +ve or -ve 4 but stem say they are positive thus =4.....suff

from two

(x-y)(x+y) = 8( 8 = 8*1 or 4*2 )

it is obvious that there is no two intigers that when added together =8 and when subtracted = 1

thus( x-y)(x+y) must = 4*2

x+y > x-y (positive intigers) thus x+y = 4 ...suff

Q3: If x is an integer, is x even?
1) x^2 - y^2 = 0
2) x^2 + y^2 = 18

from one

x^2 = y^2 we have no clue about values of y....... and zero is even

even - even = even or odd - odd = even .insuff

from two

x^2+y^2 = 18

18 is even ie even+even or odd +odd.......insuff

one and two together

2x^2 = 18

ie x^2 = 9 thus x = odd.....suff


most probably i should go to sleep
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Nothing is impossible and nothing is as bad as it seems
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Guys im still not clear....will shoot my questions on the in the evening....