IKMC 2018 - Grades 11-12 - Self-study Question 7

Question 7

Four identical rhombuses (diamonds) and two squares are fitted together to form a regular octagon as shown. How big are the obtuse interior angles in the rhombuses?

Question illustration

$135^\circ$
$140^\circ$
$144^\circ$
$145^\circ$
$150^\circ$