Hello aspirant,

I hope that you are doing absolutely great.

With reference to your above mentioned query, i would like to tell you that Yes, you can select Mathematics as option 1 subject in your GATE Examination.

You can select mathematics if you have Master's degree in any branch of Science/ Mathematics/ Statistics/ Computer Applications or equivalent are eligible for taking GATE .

Furthermore, you must choose one paper which is related to your previous study. As a student of mathematics you will not be able to choose paper chemical engineering. For any information regarding GATE visit any IIT website.

Further, you can also visit the below mentioned link to know more about the GTE Examination : https://engineering.careers360.com/exams/gate

I hope that this will help.