KUNCI JAWABAN Matematika Kelas 8 Halaman 9 Semester 2, Menghitung Luas Jari-jari Pizza Besar

Ditanya: Panjang busur (Pb)…?

Jawab: Pb = α/360 x 2πr
Pb = 90/360 x 2 x 22/7 x 7
Pb = 11 cm

- Diketahui: α = 60°
r = 21 cm
π = 22/7

Ditanya: Panjang busur (Pb)…?

Jawab: Pb = α/360 x 2πr
Pb = 60/360 x 2 x 22/7 x 21
Pb = 22 cm

- Diketahui: α = 120°
Pb = 88 cm
π = 22/7

Ditanya: r…?

Jawab: Pb = α/360 x 2πr
88 = 120/360 x 2 x 22/7 x r
88 = 1/3 x 44/7 x r
r = (88 x 3 x 7)/44
r = 42 cm

- Diketahui: Pb = 31,4
r = 100 cm
π = 3,14

Ditanya: α …?

Jawab: Pb = α/360 x 2πr
31,4 = α /360 x 2 x 3,14 x 100
31,4 = α /360 x 628
α = (31,4 x 360) x31,4
α = 18°

- Diketahui: α = 72°
Pb = 1.256 cm
π = 3,14

Ditanya: r…?

Jawab: Pb = α/360 x 2πr
1.256 = 72/360 x 2 x 3,14 x r
1.256 = 1/5 x 6,28 x r
r = (1.256 x 5)/6,28
r = 6.280/6,28
r = 1.000 cm

2. Lengkapilah tabel berikut.