For General Category cut-off varies from level 2 to level 6, and also varies for different zones in RRB NTPC CBT 2. The minimum cutoff would be 71 and the maximum goes up to 90 and varies in between so you can check according to the zone you have chosen while applying for the Post. After attempting 10-12 wrong questions out of 100 i think you will be able to clear the exam.