Q: m and n are integers and if m is multiplied by 11, the

Question

Q: m and n are integers and if m is multiplied by 11, the result is a positive prime number. What is n? 

(1) 2n is the square root of 16m
(2) n/m is an even prime integer

beckee529 · Answer

m, n = integers 
m * 11 = + prime # (can't be negative anyway)
only possible value for m = 1 (cannot be -1 or 0)

i get D although not too sure 

(1) 2n = sqrt 16m
2n = 4sqrt (1)
2n = 4*1
n = 2

(2) n/m = 2 (only possible even prime #)
n = 2m
n = 2(1)
n = 2

jimjohn · Answer

but for statement 1, couldnt n be -2 as well?

GK_Gmat · Answer

D. 

Stem tells us m = 1

stat 1:
2n = sqrt (16m)
2n = 4 sqrt (m)
n = 2 sqrt (1) = 2
Suff.

stat 2: 
n/1 is even prime integer. Only even prime int. is 2. Suff.

FN · Answer

yes i get D as well (btw your avatar is that of a puma..maybe you should change it or change your sn to gmat puma)

here is why its D..

m*11=prime number (all prime numbers are positive) the only way possible for m*11=prime number (given that n an m are integers) is that m=1;

1) 2n=sqrt(16) n=2

sufficient

2_ n/m = even prime integer..only 2 is the even prime integer...so therefore..n=2 sufficient..

sonibubu · Answer

How is sqrt(16) not +4 or -4? The answers here assume it is always positive.

kidderek · Answer

Yea, I like B

From A, n can equal 2 or -2 since BOTH 4 and -4 are square roots of 16.

Fig · Answer

No

sqrt(Something) = something positive

The fonction f(x) = sqrt(x) is defined only on x positive and gives only f(x) >= 0. f(x) cannot be equal to -4.... The confusion remains on f(z^2) = sqrt(z^2) = |z|, implying that z could be a real number that is positive or negative (Ok... 0 too

).... But this a specific kind of problem that tests, of course, if we well understand what is the function x^2, a specific function that affects 2 numbers (x) to 1 number (x^2)... Sqrt(x) is not like this... 1 number give 1 number. Thus.... sqrt(something) >= 0 and so is sqrt(16) = 4. Hope that helps

PS: I add the draw of sqrt(x)... Notice that this function remains only in the cadran I....

kevincan · Answer

I hate poorly worded questions!

11th Edition
pg. 108- prime numbers are by definition positive. Referring to a postive prime number is like referring to a married husband.
pg 114- every positive integer n has two square roots, one positive and one negative. The two square roots of 9 are 3 and -3. Only if you use that positive square root sign can you say that (1) is sufficient. This will be very clear on the GMAT.

Q: m and n are integers and if m is multiplied by 11, the

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