Triangles: sum of interior angles is 180 degree G6 worksheet Live worksheets > English. Triangles: sum of interior angles is 180 degree G6Triangles:sum of the three interior angles is 180 degree - G6. ID: 2711614. Language: English. School subject: Math. Grade/level: Grade 6. Age: 10-13. Main content: Polygons: Area of Triangles G6. Other contents: Polygons: Area of Triangles G6.