IF someone score around 250 marks in jee-main but score only 70% in 12th boards & is not in top 20 percentile, then he is not qualified for jee-advance , but can he score a good rank in jee-mains

yes u have a chance of scoring a decent rank i.e getting into an nit as weightage of baord is just 40%
mayb u shld luk for arnd 260
so prepare with full concentration and crack the exams

all the best

dont forget to approve :)