Two rectangles in a square II

A blue rectangle and a green rectangle[br]are inscribed in a square.[br][br]The overlap of the two rectangles is[br]colored yellow. [br][br]How large is the yellow area?[br][br][color=#ff0000][i][b]What questions could/would you put to your students based on this applet ?[/b][/i][/color]

Information: Two rectangles in a square II