I not that good with math but I would say C.
To find the total area of the octagon you can find the area of the rectangle that is created by the entire figure and subtract the areas of the four congruent right triangles.
(10 cm x 6 cm) - [4(1/2 x 2 x 2)]
60 cm² -8 cm² = 52 cm²
The total area of the octagon is 52 cm².
Remember:
-When multiplying numbers with decimals just forget about the decimals for a second and pretend you are multiplying a 3 digit number times a 2 digit number.
-one digit at a time. Multiply going from right to left.
First:
-Multiply the 3 with the top numbers.
-Pretend you are seeing this:
5.72 (3)
- 2*3=6. 7*3=21. (carry the 2). 5*3 +2=17. (leave the 1).
Second:
-write below and move a digit to the left.
-pretend you are seeing this: 5.72(6).
- 2*6 =12. (carry the 1). 7*6 +1=43. (carry the 4) 5*6+4=34. (leave the 3).
Third: since in the problem the decimal is placed in the hundredths only once, place the decimal in the hundredths as your solution.
Your solution should be 360.36