Stuck on Quantitative - need expert Opinion

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by Brent@GMATPrepNow » Tue Jul 14, 2015 12:15 pm
[email protected] wrote: Here is one question that I could have done the long way and found out, but I ended up taking too long and guessed.

"Which of the following is equal to the value of 2^5 +2^5 + 3^5 + 3^5 + 3^5"
Here's the original question (with solution):
2^5 + 2^5 + 3^5 + 3^5 + 3^5 = ?

A) 5^6
B) 13^5
C) 2^6 + 3^6
D) 2^7 + 3^8
E) 4^5 + 9^5
What we really have here is an algebra question that requires us to combine LIKE TERMS.

First, notice that K + K = 2K
Using the same logic, 2^5 + 2^5 = 2(2^5) = (2^1)(2^5) = 2^6

Similarly, notice that M + M + M = 3M
Using the same logic, 3^5 + 3^5 + 3^5 = 3(3^5) = (3^1)(3^5) = 3^6

So, 2^5 + 2^5 + 3^5 + 3^5 + 3^5 = 2^6 + 3^6

Answer: C

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Rich@EconomistGMAT » Tue Jul 14, 2015 1:00 pm
Hi Beth,

Just want to chime in quickly and advise you not to take TOO many practice exams. I'd be concerned that you'd burn yourself out by taking so many in one week, so try spacing them out a bit and focus on learning some of the strategies (like the explanation Brent just posted). You'll get much, much more out of focusing on training yourself to take the GMAT, rather than grinding away at practice test after practice test.

Best,
Rich

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by DavidG@VeritasPrep » Tue Jul 14, 2015 6:42 pm
I'll second Rich's advice here. The question you posted suggests that key exponent rules could be part of a summary sheet that you put together to review before taking the next exam. Do this for every question that isn't 100% clear - post them here and continue to compile a list of takeaways. Do some practice questions that will help strengthen your problem areas. Once you feel like you've mastered these areas, then take another exam. Wash/rinse/repeat.
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