tonebeeze wrote:

If n is positive, is \sqrt {n} > 100?

1. \sqrt {n-1} > 99

2. \sqrt {n+1} > 101

Can someone write out the algebra on this one, I just want to double check work. Thanks.

Even though you asked for algebra, let me point out that you don't really need algebra to solve this.

When you are considering big numbers, square roots of consecutive numbers differ by very little. e.g.

\sqrt {10000} = 100 and

\sqrt {9999} = 99.995... Square roots of even small positive numbers differ by less than 1 e.g.

\sqrt {1} = 1 and

\sqrt {2} = 1.414 - Difference of just 0.414

\sqrt {3} = 1.732 - Difference of just 0.318. The difference just keeps getting smaller and smaller.

So if

\sqrt {n-1} > 99,

\sqrt {n} will be very close to

\sqrt {n-1} and will also be greater than 99. But will it be greater than 100, we cannot say. So not sufficient.

If

\sqrt {n+1} > 101, then

\sqrt {n} may not be greater than 101, but it will definitely be greater than 100 since between two consecutive integers, the square root difference will not reach 1 (as shown above).

_________________

Karishma

Veritas Prep | GMAT Instructor

My Blog

Save $100 on Veritas Prep GMAT Courses And Admissions Consulting

Enroll now. Pay later. Take advantage of Veritas Prep's flexible payment plan options.

Veritas Prep Reviews