Hello Bhaskar!

For general aptitude part for gate exam topic is:

Verbal Ability:English Grammar,Critical Reasoning etc

Numerical Ability:Numerical Estimation,Data Interpretation etc

You can check the detailed syllabus and sample questions through this link which is issued by IIT Guwahati.

www.gate.iitg.ac.in › SyllabiPDF

Syllabus for General Aptitude (GA)

Hope it answer your concerns.

Go through the below list of some most important topics in aptitude for GATE.

• HCF and LCM
• Time 
• Work
• Mixtures
• Boat
• Train 
• Probability
• Direction
• Cube and Colors
• Blood Relation
• bar charts and pie diagram
• Critical Reasoning
• Age
• Profit and loss
• calendar

There is also verbal ability which is just simple english.