what minimum mark i ve to score in my b.tech to get admission in reputed B-school?

Plus a CAT/MAT score required

If you want admission in a reputed B School, then target a percentage above 75 in your undergrad. Also, you require 2 years of work experience to pursue your MBA from a reputed B school, as well as would require a good GMAT score above 650(preferably 700). Hope my answer has solved your query. If it

GMAT 650 or above.

you have score marks in graduation same time you have go for cat/mat/xat with preparation get high rank for excellent b schools. make sure prepare well to fight these test. best of luck