what are the total marks we write at b.arch and b.planning conducted in 2:30 to 6:00 in 2020 paper

Karthik, if you opt for both B.Arch and B.Plan for JEE Mains paper 2, you will be attempting a paper of total marks as 500.

B.Arch exam consists of 25 questions from Mathematics of 4 marks each (100 marks), 50 questions from Aptitude of 4 marks each (200 marks) and 2 drawing questions of 50 marks each (100 marks). This totals to 400 marks.

B.Plan. also has the first two sections same- 25 questions from Maths and 50 from Aptitude, summing up to 100 and 200 marks respectively in the two sections. The third section has 25 questions from Planning of 4 marks each, i.e. 100 marks. So total is again 400.

Since you have selected both the papers, you will have all the 4 sections, i.e. Maths, Aptitude, Drawing and Planning. The marks distribution would be 200 for Aptitude and 100 each for the other three sections. Hence the total would be 500 marks. Hope that helps.