Yes, solving previous years question papers of UPSC Mathematics optional subject can definitely help in improving numerical accuracy. Here's how:

1. Familiarization with exam pattern and question types:
Solving previous years question papers gives you a clear understanding of the exam pattern and the types of questions asked. You become familiar with the structure of the paper, the marking scheme, and the time required to solve each question. This helps you to strategize your approach and manage your time effectively during the actual exam.

2. Identification of important topics:
By solving previous years' papers, you can identify the topics that are frequently asked and are of high importance. This allows you to prioritize your preparation and allocate more time to these topics. It also helps in understanding the depth and breadth of each topic, enabling you to focus on the key concepts and formulas.

3. Practice of diverse numerical problems:
Previous years' question papers provide a wide range of numerical problems covering various concepts and difficulty levels. Regular practice of these problems improves your problem-solving skills and enhances your numerical accuracy. It helps in developing a clear understanding of different approaches and techniques required to solve mathematical problems efficiently.

4. Evaluation of strengths and weaknesses:
By solving previous years' papers, you can assess your strengths and weaknesses in different topics. This self-evaluation allows you to identify the areas where you need to improve and devote more time. It also helps in gaining confidence and reducing exam anxiety by familiarizing yourself with the level of difficulty and the types of questions that can be expected.

5. Time management and speed enhancement:
Solving previous years' papers under timed conditions helps in improving your speed and accuracy. It enables you to practice time management and develop effective strategies to solve questions quickly. Regular practice enhances your problem-solving skills, mental calculations, and reduces the time required to solve each question.

6. Revision and reinforcement of concepts:
Revisiting and solving previous years' papers allows you to revise and reinforce the concepts you have learned. It helps in retaining the knowledge for a longer duration and strengthens your conceptual understanding. It also aids in identifying any gaps in your preparation and provides an opportunity to fill those gaps before the actual exam.

In conclusion, solving previous years' question papers of UPSC Mathematics optional subject is an essential part of exam preparation. It not only improves your numerical accuracy but also enhances your problem-solving skills, time management, and conceptual understanding. Regular practice of these papers under timed conditions is crucial to excel in the UPSC Mathematics optional subject.