I used two apps I downloaded to my iPad, Remote Pilot and Flight Ready Test Prep. I studied primarily by taking the tests provided on both apps. Detailed explanations were given for each question asked. I took the the practice tests then zeroed in on my areas of weakness. I was probably ready in two weeks about 4 hours per day but I didn’t take the test immediately. I waited a couple of months then brushed up with practice tests for a couple of days and scheduled my actual test. Can’t remember the exact score but somewhere in the high 80’s. Not an expensive way to go.