What is the procedure for admission in iisc can I now get a admission in MBA with 80 percentile in CAT.

To prepare for CAT Arithmetic section, refer to Class 9 and 10 NCERT Math books. These books will help you recap fundamental concepts and formulae. For advance level questions, refer Arum Sharma and Nishit Sinha books recommended for CAT quantitative aptitude preparation.  

Yes, Arithmetic section is the most important topic of CAT Quantitative Aptitude as it carries maximum weightage in this section and the questions are mostly easy to crack.

Usually about 7-8 questions are asked from Arithmetic in CAT exam. It is a high scoring topic as maximum questions are doable.

Use CAT previous-year papers, standard vocabulary books such as Word Power Made Easy, and regular reading of editorials and quality articles.

Analogies are useful for improving vocabulary and word relationships. But CAT primarily focuses on Reading Comprehension and reasoning-based Verbal Ability questions.