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Statment 2: x^2-y^2=8
<=> (x+y)(x-y) = 8 = 4*2 (=8*1 not working)
Since x & y are integers, we can say than:
o x+y = 4 (1)
and
o x-y = 2 (2)
Thus (1)+(2) <=> 2*x= 6 <=> x=3
=> y=1
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
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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
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
_________________
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....
[/quote]S2: < 2 multiples of 3 ,in first 5 multiples of m.
m, 2m,3m, 4m, 5m
Again as only 3 is a multiple and less than 2 multiples then m is not a multiple of 3.
If m is not a multiple of 3 then enough to say that m is not divisible by 6 (to be divisble m to be divisible by both 3 and 2).
Sufficient.
Answer: B.
---------------------------
The second statement was
2) Fewer than 2 of the first 5 positive integer multiples of m are multiples of 12 (not of 3)
Hass can you explain the second point with respect to 12...
Are there any tricks to get to these questions.......
Thanks guys I got the other two questions.....as per your explanations. Answer for Q2 is D and for Q3 it is C.......