What is the area of a regular octagon with an apothem of 9.3 cm and a side length of 7.7 cm?

Octagon is equal in area to 8 rectangles, length 9.3, width 7.7/2 ie 3.75. Area of each of these is 35.805 sq cm so total area is 286.44 sq cm.

Alternatively you can mutiply the square of the apothegm by 3.314 (8/tan 67.5) which gives 286.6.