PSLE
OFGHJ is part of a circle of radius 15 cm. OFH and OGJ are quarter circles. The area of the shaded part OGH is 75 cm² and the perimeter of the shaded part OGH is 60 cm. For each of the following, use the calculator value of π to find:

1. the area of the figure OFGHJ, correct to 1 decimal place,
2. the perimeter of the figure OFGHJ, correct to 1 decimal place.

(a)
Area of the quarter circle
= ¹₄ x π x 15 x 15
= 56.25π cm²

Area of sector OHJ
= 56.25π - 75

Area of figure OFGHJ
= 56.25π + 56.25π - 75
= 112.5π - 75
≈ 278.4 cm² (Correct to 1 decimal place)

(b)
Length of arc GH
= 60 - 15 - 15
= 30 cm

Length of the arc of the quarter circle
= ¹₄ x 2 x π x 15
= 7.5π cm

Length of arc HJ
= (7.5π - 15) cm

Perimeter of the figure OFGHJ
= 7.5π + 7.5π - 15 + 15 + 15
= 15π + 15
≈ 62.1 cm (Correct to 1 decimal place)

Answer(s): (a) 278.4 cm²; (b) 62.1 cm