11th and 12th Maths are not required for getting chance through CAT in IIM. In quantitative aptitude section you will get questions from arithmatic, algebra and geometry. Questions are based on 10th level mathematics but if you have knowledge about 11th and 12th level of mahematics then you will get an advantage over it. 

Wish you good luck!

It is not compulsary. But if you have'nt had maths in your 11 and 12, you are likely to face problems in your preparation for CAT. So you must give in a lot of extra effort to compensate for the same.

All the best

For appearing to CAT - a management entrance undergoing through all over India, Requirement of Maths in 11and 12th is not compulsory.But you are definitely going to face problems during preparation of CAT .As Quantitative Aptitude - One of the three sections of CAT plays a significant role in CAT percentile.And even If you get good scores in CAT it will create a problem during GD PI of IIMs due to absence of Mathematics in 11th and 12th.

I hope it helps.