Review of Grades 5–8: triangles and quadrilaterals
Answers are for parents and teachers.
1
Two angles of a triangle are 35° and 85°. What is the third angle (degrees)?
60
2
One of two adjacent angles of a parallelogram is 40° larger than the other. What is the smaller angle (degrees)?
70
3
The midlines of a triangle are 5 cm, 6 cm and 9 cm long. What is the perimeter of the triangle (cm)?
40
4
An exterior angle at the base of an isosceles triangle is 110°. Find the angles of the triangle.
70°, 70°, 40°
5
Explain with a diagonal why the angles of a quadrilateral add up to 360°.
A diagonal splits the quadrilateral into two triangles whose angle sums are 180° + 180° = 360°.