Dave rallied to avoid that mistake on the GMAT, however, and all of these elite GMAT instructors want you to do the same. You\u00a0 have to pay attention to key words on the GMAT.\u00a0 Consider this example:<\/p>\n
If a positive even number n is not divisible by 3 or 4, then the product (n + 6)(n + 8)(n + 10) must be divisible by which of the following?<\/p>\n
I. 24<\/p>\n
II. 32<\/p>\n
III. 96<\/p>\n
A. None
\nB. I only
\nC. II only
\nD. I and II only
\nE. I, II, and III<\/p>\n
This question offers several constraints for the possible values of n, and missing any one of those key traits will likely cost you the question.\u00a0 N must be:<\/p>\n
- \n
- Positive<\/li>\n
- Even<\/li>\n
- Not divisible by 3<\/li>\n
- Not divisible by 4<\/li>\n<\/ul>\n
As this question was discussed by aspiring MBA students in a forum\u00a0 thread earlier this week, the most common reason for someone to miss it was that they missed that small word \u201ceven\u201d; they\u2019d plug in a number like 1 or 5 for n \u2013 numbers that ARE NOT possible given the constraints \u2013 and incorrectly believe that the answer is E.\u00a0 In actuality, however, these constraints taken together mean that the only possible values for n are numbers like:<\/p>\n
2, 10, 14, 22, 34\u2026<\/p>\n
And for these numbers, the product of (n+6)(n+8)(n+10) is divisible by all of the above.\u00a0 We are\u00a0 assured that, if n is even but not divisible by 4, then n + 6 and n + 10 WILL BE divisible by 4 (try it: 2, 6, 10, 14\u2026all of these numbers are even but not divisible by 4; add 6 and you get 8, 12, 16, 20 \u2014> all divisible by 4).\u00a0 So the product will give us:<\/p>\n
(n + 6)(n + 8)(n + 10)<\/p>\n
Divisible by 4 * Even * Divisible by 4<\/p>\n
Providing prime factors of (at minimum):<\/p>\n
(2*2)(2)(2*2) \u2013> the product must be divisible by 2^5.<\/p>\n
And because we have three consecutive even integers, exactly one will be divisible by 3 (try it:\u00a0 2, 4, 6<\/strong><\/em>, 8, 10, 12<\/strong><\/em>, 14, 16, 18<\/strong><\/em>\u2026 \u2013 every third value is divisible by 3).<\/p>\n
So we know that the product is divisible by 3*2^5, and to be divisible by I, II, and III we need:<\/p>\n
24: 3*2^3 (check!)<\/p>\n
32: 2^5 (check!)<\/p>\n
96: 3*2^5 (check!)<\/p>\n
Regardless of how comfortable you feel with prime factorization and number properties, however, if you miss the term \u201ceven\u201d or \u201cnot\u201d (in \u201cnot divisible by 4\u2033) you\u2019ll get this question wrong.\u00a0 The GMAT requires you to pay attention to those details, and to have that extra sense for which words are likely to be gamechangers \u2013 words like:<\/p>\n
Definitions of numbers:<\/p>\n
Even, Odd, Nonzero, Nonnegative, Integer, Positive, etc.<\/p>\n
Parameters:<\/p>\n
All, Some, None, Not, Not All, etc.<\/p>\n
Author\u2019s intent:<\/p>\n
However, Also, Therefore, etc.<\/p>\n
As you make mistakes \u2013 and rest assured you WILL make mistakes \u2013 in practice, note the subtle wordplay that causes you to do so, and heighten your awareness for those terms.\u00a0 Unlike Chris Farley, you can recover from GMAT mistakes with all ten fingers intact (this will help with the AWA essay), but you would be wise to learn from them.\u00a0 The devil is in the details, and the GMAT loves to embed important details in what may look like subtle wordplay. Word to the wise: watch those words carefully.<\/p>\n
Heads up! Prices will rise for Veritas Prep\u2019s 42-hour GMAT prep<\/a> courses on July 1! Enroll now to lock in today\u2019s lower prices and save up to $180 (use discount code GMATC10)!<\/p>\n
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