GMAT Tip: Just When You Think You’re Done, Keep Going
Many test takers preparing for the GMAT get frustrated with questions in the quantitative section, often providing responses like “I took advanced math in college!” and “I did great on my SAT math, what gives?!”
The GMAT Quantitative section is a tricky beast, with one key theme to the questions – just when you think you have done enough work to solve the problem, you still have more work to do. Test takers often don’t recognize this key strategic mindset for problem solving and data sufficiency questions, instead feeling frustrated because they’ve selected what they thought was a cut and dry answer, or were not even to find an answer that matched their hard work among the ones provided.
Let’s take this question for example:
What is 3^8 + 3^7 – 3^6 – 3^5?
- None of the above
Test takers who have been doing a good deal of practice will recognize that this a factoring question and that the GMAT assessing understanding of multiplication of exponent rules. The next step we take with the problem is to factor out a 3^5:
3^5(3^3 + 3^2 – 3^1 – 1)
From there, we should recognize that the 1 in the far right section of the parentheses throws our bases of 3 off and we might want to go ahead and do the math inside the parentheses – 27 + 9 – 3 – 1 = 32.
In evaluating the answer choices, we should recognize that we are looking for another base raised to a power – 32 is the same at 2^5.
Therefore, our answer is (3^5)(2^5).
While we should feel pretty confident that we have gotten to the right answer, when looking at the answer choices, many test takers answer (E) none of the above.
But, this is a classic GMAT quantitative example of “when you think you’re done, just keep going!”
The GMAT is testing your understanding of factoring and multiplication of exponents ONE more time – in fact, 3^5*2^5 is the same at (3*2)^5, as in 6^5, making the correct answer choice (D).
Keeping this strategic mindset in answering and evaluating answer choices will take you to the next step of getting trickier GMAT quantitative questions correct.
The above GMAT Tip comes from Veritas Prep. Since its founding in 2002, Veritas Prep has helped more than 100,000 students prepare for the GMAT and offers the most highly rated GMAT Prep course in the industry.