Improving from low scores
First of all, we would like to insist that scoring low on your first attempts is not a major issue at all, it is very normal. In fact, some of us at IGotAnOffer were scoring low on our first attempts at the McKinsey PST and BCG Potential Test.
If you are here, you've probably already solved a few tests. What we suggest now that you have solved a few tests is to look ver carefully at their solutions, and to then redo each of them. The second time you do them, you should focus on answering correctly any questions that you missed the first time, and on answering faster any questions that you got right. This second round should take your score to about 70-80%.
Once this is done, look at your mistakes again, and check whether some of these are the same as the first time you tried the test. If they are, then spend extra time looking through the solutions of those, and try solving these specific questions again and again until you get them right, in as little time as you can.
Finally, do the tests a third time. This should now bring your score between 90-100%. You should then feel confident that you know how to answer each type of question, that you understand the reasoning behind all of them, and that you are able to do the calculations quickly. This will indicate that you are ready to solve the real McKinsey PST / BCG Potential Test.