The chapter that is usually completed early in Class 10 Mathematics is "Surface Areas and Volumes". This chapter deals with the calculation of the surface areas and volumes of different geometrical shapes such as cubes, cuboids, cylinders, cones, and spheres. Here's why this chapter gets completed early:

1. Basic Concepts: The chapter starts with the basic concepts of surface area and volume, which are easy to understand. Students can quickly grasp the concept and move on to the next topic.

2. Formulas: The chapter involves the use of formulas to calculate the surface area and volume of different shapes. Once students understand the formulas, they can easily apply them to solve problems.

3. Practice: The chapter provides a lot of practice problems, which helps students to reinforce their learning and gain confidence in the subject.

4. Real-life Applications: The concepts taught in this chapter have real-life applications, such as calculating the volume of a water tank or the surface area of a room. This makes it easier for students to relate to the subject and understand its relevance.

In conclusion, "Surface Areas and Volumes" is a chapter that gets completed early in Class 10 Mathematics because of its basic concepts, formulas, practice problems, and real-life applications. Students can quickly grasp the concepts and apply them to solve problems, which helps them to move on to more complex topics in the subject.