• 360º ÷ 8 [Accept answer to a) ÷ 8].
• Exterior angles sum to 360º.
• 180º - 135º or angles on a straight line if c)i) and c)ii) both correct.

easy
moderate

c)

i)
ii)

135 [Accept 180 - answer to b) i)].
Any 1 of:

• 180º - 45º.
• [Accept 180º - answer to b) i)].
• Angles on a straight line (sum to 180º).
• Sum of interior angles = 1080º.
• 180º (n - 2) = 180º × 6 = 1080º.
• 1080º ÷ 8 = 135º.
• Number of internal triangles × 180º ÷ 6.
• 90º + 45º if b)i) and b)ii) both correct.
• Other equivalent explanations.

easy
moderate

Teaching and learning:

This assessment resource is about the interior angles of a octagon. Ideally, students will have already explored the relationship between the number of corners (angles) of a shape and developed a conjecture and then a generalised rule about the relationship between the number of sides of a shape (polygon) and the sum of interior angles. For example, they could explore a range different (regular and irregular) variations of common polygons, and measure and sum the interior angles (noting the relationship with the exterior angles), and then look at the pattern to develop a conjecture, followed by a generalised rule about sum of interior angles = number of sides x 180°.