how many questions i need to attempt for CAT?

Depends on what you target ....if it is 99 then for for at least 80, 60 for 90 and 50 foe 80

hat percentile ll,i get if i attemp 20 question?

according 2013 cat,
75% marks =99.9
67%=99.0
55%=97.5
50%=95+
these are the amount of marks u need to score... now how many qus will you attempt is depends on your accuracy...