There are about 14-17 formulas, which span schedule and cost management, general planning and estimation, business case development and a handful of other areas.
The memorization of the formulas is routine; a handy trick is to write one formula a few times during the day, and when you can write that without hesitation, add another, then another, and so on. This is only short-term memorization, though.
To go further, you need to review why the formula exists, and what type of questions the results answer. For this, you’ll have to understand interpretation. For instance:
Benefits-cost-ratio (benefits / cost) is the size of the benefits relative to the size of costs. It answers the question, “What is the size of benefits across multiple projects, regardless of costs?”
The interpretation of the Benefits Cost Ratio is:
“We expect x.xx benefits for every $1 investment of cost.”
You see how the formula is used, you understand the meaning of the result, and you can interpret. If you review this across 5 or so practice question that bring this up, you will soon not only memorize but understand how the formula is used in business and for the exam - solving problems.