Yes, pretty much all quant (esp. lower level) questions fall into patterns.
The harder the question, the tougher it is to spot the pattern since the fewer of them are in the OG.
Finally for the 750-level questions, you are looking into pretty unique ones that you probably will not have encountered.
So, what does it mean for our prep and strategy?
Well, 1) that means that if you are aiming for 600-650 level, you can do it by memorizing patterns
2) Getting above the 650-level, you are most likely to hit some patters you won't know thus relying just on patterns is not going to get you too far with those questions and you should emphasize fundamentals and basics more at this level (though often people go into the test/question mode by this time)
3) It is faster to learn by covering all Quant areas in guidebooks than solving thousands of questions in search of patterns
4) It is important to spot patters as it can save you a LOT of time
5) It is possible to get a 750 without ever opening OG, but it is not recommended. You do want to go through it, esp for the verbal part to train your ear on the CR/RC, and SC.
Hope this helps!
P.S. If you are starting to spot patterns that's because they exist and please do - it is very helpful even for the harder questions that often consist of 2-3 diff patters.
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