Is N divisible by 7? 1 N=x-y, where x & y are

Question

Is N divisible by 7?

1> N=x-y, where x & y are integers
2> x is divisible by 7, & y is not divisible by 7.

The answer is c, its say's by combining we can say x is the multiple of 7, but y is not multiple of 7. The difference between x & y NEVER be divisible by 7 if x is divisible by 7 but y is not ( this part I am unable to understand

- is there some rule that i need to learn here or a logic to follow)

Regards
Divakar KN
:flower

- is there some rule that i need to learn here or a logic to follow) Regards Divakar KN :flower

chix475ntu · Answer

writing st 2 in equations 
x = 7a
y = 7b + c (where c interger and 0< c < 7) .... as y is not divisible by 7, there would be a reminder when y is divisible by 7

N=x- y = 7a - 7b - c = 7 (a-b) - c

as you can see from the above, there would be a reminder when N is divided by 7

HTH

swethar · Answer

Ans. C

Using (1):

N=x-y and since we do not know any of these, INSUFFICIENT

Using (2):

x=7k, y=7l+m

but we do not know how x and y are related to N, so INSUFFICIENT

Using (1) and (2), we have:

N = 7(k-l) - m 
and N/7 = (k-l) - m/7 => we always have a reminder and so, N is not divisible by 7

BarneyStinson · Answer

DS questions of this kind demand a substantial answer, a strong YES or NO. If you can prove either of them based on the two given statements, you have nailed the question. Here, both the statements are required to prove strongly that N can never be divisible by 7. That's it - PERIOD!!

divakarbio7 · Answer

Thank you all :-D

amma4u · Answer

Is N divisible by 7?

1> N=x-y, where x & y are integers = x and y can be any value. insufficient.
2> x is divisible by 7, & y is not divisible by 7 = using this no connection to N.

BOTH = let's take x=7 & y=3
therefore, N=x-y=1-3 = N is not divisible by 7
if x=7 and y= 7 = N=0/7 not divisible. So, taking any value using both it does not satisfy that N/7.

jeeteshsingh · Answer

Easiest way....

S1 alone is not sufficient as no idea abt x and y
S2 alone is not sufficient.. as no relation with N
Hence either C or E...
N=x-y and x is divisible by 7 and y is not...

\frac{N}{7}=\frac{x-y}{7}=\frac{x}{7}-\frac{y}{7}=   Integer (as X is divisble by 7) - non integer (fraction as y is not divisible by 7) = non integer.

Hence not divisible. Therefore C.

Is N divisible by 7? 1> N=x-y, where x & y are

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