Numerical aptitude is a part of your aptitude test. It checks your understanding of numbers and application of various mathematical operations.
To solve any numerical, firstly, you need to understand and analyze the question. Develop the skill of understanding the question. Solving any question, without understanding what the question is saying, is tough. Understanding of question means extracting as much information from the question as needed. Hence, realizing the relation of each of these bits of information.
After understanding the question, you need to think of a suitable method to solve the numerical. Questions asked in the Numerical Aptitude are mostly based on general mathematics. However, no specialization is needed in solving mathematical questions. Therefore, basic concepts are enough. What matters the most is not just concepts, but your ability to apply these basic concepts to bigger problems.
A proper time is needed to set every day to practice Numerical Ability. Practicing mock tests through Top Mock Test app has already proved beneficial in preparation. Hence, try solving questions from previous year question papers. This will build confidence in you to deal with any numerical questions.