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GMAT Tips: Emphasizing Arithmetic

Today’s GMAT tip comes to us from Veritas Prep.  In today’s blog post, they explain the importance of emphasizing arithmetic while taking the GMAT.  Read on to see what they have to say!

In this election seasons most-Tweeted-about speech, Bill Clinton talked about a question that he’s frequently asked in interviews, and one of his signature lines of the speech was his one-word response: Arithmetic.

Now, whether you agree with Clinton’s assertion that the solution to many of the complex American budget problems is that one word, Arithmetic, is a discussion for another blog. But what cannot be disputed is that Arithmetic is the solution to some of the most complex GMAT problems you’ll see.

The GMAT is a test on which the most complex problems often have the simplest solutions, at least for those willing to reason through them. Students often chase the “hardest” content items available on the test and breeze past or overlook-entirely the most useful items.
What is the sum of the digits of integer k, if k = (10^40 – 46)

(A) 351
(B) 360
(C) 363
(D) 369
(E) 378

While this may look like a monster problem, it’s really just one of arithmetic. 10^40 is an insanely large number, but conceptually it’s not much different from 10^3 (i.e. 1000). If you test this relationship with a few small numbers, you can get a good look at what k will look like. For example:

10^2 – 46 = 100-46 = 54
10^3 – 46 = 1000-46 = 954
10^4 – 46 = 10000-46 = 9954

Do you see the pattern? Every time we add one to the exponent, we add another 9 to the solution. And the number of digits in the solution is always the same as the exponent itself. So for this problem, where the exponent is 40, k will have 40 digits: a 5, a 4, and the other 38 are 9s. And since 5 + 4 is 9, then really we’re just adding up 39 9s. And 39*9 is 351 (or you can just see that it will end in a 1, and only A matches).

Now, this problem looks to many to be complex. But heed Bill Clinton’s advice – it really just comes down to Arithmetic. The “hardest” math on this problem is taking 10^4, or multiplying 39*9. “Special” math skills are infrequently required or rewarded on the GMAT – sound fundamentals in Arithmetic, Algebra, and a few conceptual rules of Geometry, Probability, and Statistics are generally all you need, provided you supplement those with reasoning and ingenuity.

So to succeed on the GMAT? Make sure you emphasize Arithmetic, and look for opportunities to simplify complex problems with Arithmetic.

For more information on Veritas Prep, download Clear Admit’s independent guide to the leading test preparation companies here. This FREE guide includes coupons for discounts on test prep services at ten different firms!

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Posted in: GMAT - Quantitative, GMAT Tips

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