Using Assignment Groups allows you to organize the assignments in your course.
Click the Assignments link.
Click the Group menu for creating assignment groups.
Type the Assignment Group title in the Group Name field [1]. Click the Save button [2] to create the Assignment Group.
View the Assignment Group details by clicking the Group menu link by the Assignment Group name.
For creating the Grading Rules click the Edit option present in the created Assignment Group.
For each Assignment Group, you can Drop the lowest or Drop the Highest x number of grades. You can also specify which Assignments should never be dropped from the Assignment Group calculation and click Save button for apply changes.