Seconded. The
Manhattan GMAT books are great. For you, probably the ones on Number Properties (Guide 5) or Fractions, Decimals, & Percents (Guide 1) would be the most helpful. You may also want to make flashcards. Having prime numbers, perfect squares, fraction to decimal conversions, etc. down cold will definitely help you get faster. So many problems rely, directly or indirectly, on prime factorization. And if you know your multiplication table and the primes up to, say, 47, down cold, you will see the factorizations more quickly and know for sure when you’re done. A lot of the prep companies have their own flashcard decks that you can use (not sure if
EmpowerGMAT does), but it’s better for you to make your own. There are studies that show you understand/remember something better when it’s in your own writing, and the act of writing itself helps get it in your memory. Or, you can use flashcard software like Anki:
https://apps.ankiweb.netOne thing that’s nice about Anki - it uses a spaced repetition system. There’s a whole bunch of science behind how often you need to see a fact to remember it. Basically, Anki’s spaced repetition system will show you a card more often when you’re first learning it and less often later on. It will show it to you more often if you get the card wrong or are unsure about it. So you don’t need to keep track of which cards you need to work on that day or what you’re shakier on. It keeps track for you.
Things I’d recommend putting on the cards:
fractions to decimal conversions for basically all fully reduced fractions with single digit denominators
approximations for \(\sqrt{2}, \sqrt{3}, \sqrt{5}\) : (\(\approx{1.4}, 1.7, 2.2\))
perfect squares up to 15 (\(1^2=1\), \(2^2 =4, … ,15^2 = 225\))
perfect cubes up to 10 (\(2^3=8, …. , 10^3=1000\))
prime numbers up to 47: 2,3,5,…47
anything else you think you need to work on/memorize.
-V.