HI 

There is no specific guarntee in the above question. If you get 45 in chemistry, its a fair marks and it would be added with the practical marks as well. And same for physics. Then you can pass overall. 

From last year, the teachers are more strict regarding paper checking and often are restircted to give grace marks. This was ordered and issued by the HRD ministry of India and was legalised from year 2018.

hope this answers your query, all the best

cheers!