Solution (1) using angles of sectors:
Area of A = pi r^2 x 90/360 = 4.9
Area of B = pi r^2 x 270/360 = 14.2
Check: Area of A/B = 4.9/14.72 = 1/3 (as given)
Solution (2) using given info:
Area of B + Area of A = area of circle
Area of B + 1/3 Area of B = 3.14 * (2.5)^2 = 19.625
4/3 Area of B = 19.625
Area of B = 3/4 * 19.625
Area of B = 14.72
Area of A = 1/3 * 14.72 = 4.9
There is more solutions to this problem , like polar coordinate integration , and so on. for more just request.
