So a Q46 is a solid quant score. It's not 'elite,' but it's very respectable. It shows you have a solid grasp virtually all the foundations. You're hardly ever missing average to above average difficulty questions, and on the harder questions, you're probably going 75% right. The very hardest questions are probably in the 30-40% range.
So how to improve? Your instinct will be to focus on the hard stuff, and you should (make sure you pick up the Advanced
Official Guide; MPrep also has an advanced quant book you may find useful), but don't neglect the easy stuff either.
To score a 48+ in quant:
--Average and slightly above average questions you should be able to get right, basically 100% of the time, in about thirty seconds (not that there isn't the occasional exception, but by and large, that's where you need to be).
--The 'hard' questions need to stop feeling hard, by and large. You should recognize a solution path, possibly several, to most of these questions within 25 seconds, and virtually always get them right.
--You're not allowed "Silly mistakes" (maybe one or two a section). If arithmetic costs you even one question on a quant section, you need to practice your arithmetic.
--And then, yes, the hardest questions need to be more accurate than 30-40%. Dig into the advanced quant for that.
First note that improvement at any level will
be in the ways mentioned in this post, so when you're reviewing a quant question, pull out your scalpel and really figure out where you need to improve.
Make sure you have a full Problem Solving toolkit:
and that you're not relying on pure algebra, all the time.
On PS questions you miss, I highly recommend, in your review, that you build the 'inference chains' of that problem:
and figure out which arrows give you the most grief, and why.
A lot of hard questions force away a traditional, algebraic solution path. Make sure you're developing new strategies for certain topics you might not have needed before (e.g. number line visualizations for inequalities/absolute value questions; a 'teeter totter' approach for weighted averages).
And, of course, if you can afford it, a private tutor can help snipe the places that are costing you the most points, and can help you learn and practice the strategies you need to get those sky-high quant scores.