How many minimum number of questions need to be corrected from each section to get a fair score(85-90%)?

The nature of CAT is very dynamic because of the changing difficulty level and changing patterns. In some of the past year getting 50% percent of questions right could help you score 90 percentile or more while in some other years getting 50% percent of questions right could help you score only 70-80 percentile or sometimes lesser than that. Also the section level difficulty also varies amongst the three sections and you can get different percentile in 3 sections if you attempt 50 percentile. For example in last years CAT the LRDI section was percieved tougher and you could score 90 percentile by getting 50% percent of questions right.

Hence it is always suggested to select questions which you can solve correctly and then try to solve them with complete accuracy. If the section seems relatively easy then try to attempt maximum questions. Try to understand the difficulty level of paper and solve accordingly.