180. Circle angles

In the diagram, point O is the centre of the circle.
Determine α.


179. Box volume

The length and width (breadth) of a rectangular parallelepiped (cuboid) are each decreased by 5%, and the height is increased by 4%.  By what percentage does the volume (capacity) change?


178. Quadrilateral query

In the diagram, the area of ABC is 72 cm².  Point D divides side AB in a ratio of 1:3, and point E divides side BC in a ratio of 1:2.  Determine the area of quadrilateral ADEC.