Hi jkolachi,
Believe it or not your situation is quite common amongst GMAT test-takers. GMAT success is related, in part, to a) one's ability to quickly recognize the concepts being tested in a given GMAT question and b) being able to then quickly attack that question. However, developing those abilities does not come overnight. To gain such abilities, you might consider a study routine that consists of focused learning and practice. For instance, I imagine that at some point you studied Number Properties. However, when studying that topic, were you able to first learn everything possible about that topic? Concepts such as LCM, GCF, units digit patterns, divisibility, remainders, etc? After that, were you able practice with a lot of questions (50 or more) just on Number Properties to reinforce what you learned? If not, it’s possible that you did not fully learn that topic and thus have been unable to efficiently attack all Number Properties questions that you encounter. Although Number Properties is just one example, ideally you should follow this method of focused learning and practice for all GMAT quant topics.
Let’s further highlight this idea with a basic quant example question.
20^2 + 21^2+ 22^2+ 23^2+ 24^2+ 25^2 = ?
A) 3,055
B) 2,060
C) 3,066
D) 3,704
E) 3,077
Upon seeing this question, what is the first thing that comes to your mind? Do you want to grab a calculator and add up the values in the expression? Are you spending 20 to 30 seconds thinking about how this question should be solved? Or do you quickly recognize that you are likely being tested simply on patterns in units digits?
If you were able to recognize that you are being tested on patterns in units digits, it’s a good sign that you have mastered (or are at least on the road to mastering) some concepts related to units digits, and, in the bigger scheme, how to recognize and attack a quant problem.
Solution:
Because each answer choice has a different units digit, instead of finding the actual sum, we can just find the units digit of the sum. Let’s use the units digits of each square to determine the units digit of the sum.
- The units digit of 20^2 must be 0, since 0^2 = 0
- The units digit of 21^2 must be 1, since 1^2 = 1
- The units digit of 22^2 must be 4, since 2^2 = 4
- The units digit of 23^2 must be 9, since 3^2 = 9
- The units digit of 24^2 must be 6, since 4^2 = 16
- The units digit of 25^2 must be 5, since 5^2 = 25
With this, we can sum the units digits: 0 + 1 + 4 + 9 + 6 + 5 = 25. Thus, the units digit of the correct answer is 5.
Answer: A
Although this is just one example (of many), you see that you must have the tools in your toolbox to efficiently attack each GMAT quant question that comes your way.
If you would like to practice more questions similar to the one above, I welcome you to take my free
37-question quant diagnostic. After completing the diagnostic, you will be provided with a detailed analysis of your proficiency level in all GMAT quant topics, as well as an opportunity to discuss your diagnostic results with me or another
TTP instructor/coach.
If you have any further questions, feel free to contact me directly. Keep working hard! You’ll reach your goal!
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27 Oct 2016, 16:18
