Many candidates were unable to interprete the diagram correctly. While some treated it as a circle, others considered it to be a sector but they were asked to find the perimeter of a segment of a circle. AB is a chord with length 100m. This served as a clue to finding the angle (x) subtended at the centre by the arc AB as shown below. Hence, length of chord AB = 2r Sin x/2 where r = radius of the circle.
Thus, 100m = 2(56) Sin x/2 >> Sin x/2 = 100/112 and x = 126.48°.
The angle which the arc AB subtends at the centre would be
360 – 126.48 = 233.52°. The perimeter of the shape would also be
233.52 x 2 x 22 x 56 + 100 = 328m to the nearest metre.
360 7 1
