i am a BTech student graduating with aggregate around 55%, so can i get into top 10 b-schools in Indian (excluding iim) ? if yes how much should i score in cat ?

You can definitely get a tier 1 B School. You'll just have to perform exceptionally well in CAT and in the subsequent selection rounds. If you belong to general category then you need to have a minimum of 50 percentile in graduation in order to appear for CAT. But during the final selection some weightage is definitely assigned to the academic records so try to do well during the entrance exam and interviews. Excluding IIMs the best B schools are

• JBIMS Mumbai (CAT percentile required = 99.99)
• SPJIMR Mumbai (CAT percentile required = 98 and you can get a call at 85 percentile also during their profile based shortlisting process if you've a good profile and a minimum of 2 years work experience)
• MDI Gurgaon (CAT percentile required = 95-96)
• XLRI Jamshedpur (XAT percentile required =99.99)
• FMS Delhi (CAT percentile =99.99)
• NITIE Mumbai (CAT percentile = 99)
• Department of Management Studies, IIT Delhi (CAT percentile =95)
• SIBM Pune (SNAP percentile required =98)
• NMIMS Mumbai (NMAT scores required =above 210)
• TISS Mumbai (TISSNET cutoff = more than 76)