In the figure above, arc QRO is a semicircle. What is the area of the circle with center O?
1) The area of the triangle PQO is 30.
2) The length of QRO is 2.5Ï€.
The OA is C.
To calculate the area of the circle with center O, we need to know the radius PO.
1) 1/2 *QO * PO = 30. QO unknown => no way to know PO.
2) know QO. But how to know PO? No way.
(1) + (2) => know QO => know PO => know area. Hence C is the correct answer.
