Quantitative

Hi John fran kennedi,

For anyone who's interested, this question can be found in the OG:

GMAT2016 - page 184, question 220
OG13/GMAT2015 - page 183, question 216

TESTing THE ANSWERS (the approach that Mitch used) is perfect for this question, so I won't rehash any of that work here. If you've looked at the explanation in the OG, then you'll notice how it focuses on the longer, technical math involved - and that approach is not always practical on Test Day (when the clock is ticking). As you continue to study, you should look for opportunities to use Tactics, pattern-matching, etc. to your advantage.

GMAT assassins aren't born, they're made,
Rich

Hi John fran kennedi,

You'll likely improve, speed up, etc. as you continue to study, but there are also resources that can help you to improve.

1) How long have you been studying?
2) What resources have you been using?
3) What is your goal score?
4) When are you planning to take the GMAT?

GMAT assassins aren't born, they're made,
Rich

John fran kennedi wrote:Some of explanations from the OG book is complicated for me, that's why I do need a faster approach to solve every question and to save the time.

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The various Official Guides are great resources for official practice questions, but they're not very comprehensive when it comes to instruction or the way the solutions are presented (often algebra-heavy). To perform well on the GMAT, you need to learn all of the core concepts AND you need to learn GMAT-specific strategies for answering questions quickly and accurately. In my opinion, the Official Guides do not provide this level of instruction.

Lucky for you, this site is packed with companies/people who can provide the instruction you need

Cheers,
Brent

Hi John fran kennedi,

I've sent you a PM with some suggestions.

GMAT assassins aren't born, they're made,
Rich