GMAT.QR.0251
Book Question: 251
If n is positive, is n > 100 ?
n − 1 > 99
n + 1 > 101
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements (1) and (2) TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are not sufficient.
You Answered Incorrectly.
Algebra Radicals
Determine if n > 100 or equivalently, if n > (100)(100) = 10,000.
Given that n − 1 > 99 or equivalently, n − 1 > (99)(99), it follows from
( 99 ) ( 99 ) = 99 ( 100 − 1 ) = 9,900 − 99 = 9,801
that n − 1 > 99 is equivalent to n − 1 > 9,801,or n > 9,802. Since n > 9,802 allows for values of n that are greater than 10,000 and n > 9,802 allows for values of n that are not greater than 10,000, it cannot be determined if n > 10,000; NOT sufficient.
Given that n + 1 > 101 or equivalently, n + 1 > (101)(101), it follows from
( 101 ) ( 101 ) = 101 ( 100 + 1 ) = 10,100 − 101 = 10,201
that n + 1 > 101 is equivalent to n + 1 > 10,201, or n > 10,200. Since 10,200 > 10,000, it can be determined that n > 10,000; SUFFICIENT.
Statement 2 alone is sufficient.
I am unable to understand the explanation on Wiley's website. I think that it is more than 700 level question. Can anyone help with this one!
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