Reciprocal of n

[binaras]

Hi,

Need help answering the question in the attached screen shot.

Thanks

[GMATGuruNY]

If n denotes a number to the left of 0 on the number line such that the square of n is less than 1/100, then the reciprocal of n must be

A. less than -10
B. between -1 and -1/10
C. between -1/10 and 0
D. between 0 and -1/10
E. greater than 10

Let n = -1/20.
This works because (-1/20)² = 1/400, which is less than 1/100.
In this case, the reciprocal of n = -20.

Only answer choice A is viable:
-20 is less than -10.

The correct answer is A.

[[email protected]]

Hi binaras,

GMAT questions often include a number of details/rules that you have to follow to get to the correct answer. If you have trouble understanding how everything "works", it often helps to break down the prompt into 'pieces' and work through each piece one at a time (taking notes, doing calculations, etc.).

Here, we're told that N is a number to the LEFT of 0 on the number line....

So, N is NEGATIVE

Next, we're told that the SQUARE of N is LESS than 1/100

So, N^2 < 1/100

Conceptually, this might seem a little tricky, so I'm going to list some examples for comparison (and we can "hone in" on what N could be...):

(-1)^2 = 1
(-1/2)^2 = 1/4
(-1/10)^2 = 1/100

Notice the pattern here....as the denominator gets bigger, the value of N^2 gets smaller. This tells us that N falls into a range of possible values:

-1/10 < N < 0

Finally, we're asked for the RECIPROCAL of N....

In real simple terms, 'reciprocal' means "flip the fraction over." For example, the reciprocal of 2 is 1/2; the reciprocal of 3/5 is 5/3, etc.

Given the range of possible values for N, the RECIPROCAL of N must be.....

-10 > N > -infinity

Final Answer: A

GMAT assassins aren't born, they're made,
Rich