1. keliling lingkaran 220 cm. luas juring dengan sudut pusat 90 derajat adalah... 2. keliling lingkaran yang luasnya 2464 cm2 adalah... 3. keliling lingkaran =

1.
Penyelesaian:
Diket.:
K = 220 cm
α = 90°
Ditanya:
Luas juring = ....?
Jawab:
2πr = K
2 × 22/7 × r = 220
44/7 × r = 220
r = 220 : 44/7
r = 220 × 7/44
r = 1.540/44
r = 35 cm

Luas juring
= α/360° × πr²
= 90°/360° × 22/7 × 35²
= 1/4 × 22/7 × 1.225
= 26.950/28
= 962,5 cm²

2.
Penyelesaian:
Diket.:
L = 2.464 cm²
Ditanya:
K = ....?
Jawab:
πr² = L
22/7 × r² = 2.464
r² = 2.464 : 22/7
r² = 2.464 × 7/22
r² = 17.248/22
r² = 784
r = √784
r = 28 cm

K = 2πr
K = 2 × 22/7 × 28
K = 1.232/7
K = 176 cm

3.
Penyelesaian:
Diket.:
K = 22 cm
α = 80°
Ditanya:
Panjang busur = ....?
Jawab:
2πr = K
2 × 22/7 × r = 22
44/7 × r = 22
r = 22 : 44/7
r = 22 × 7/44
r = 154/44
r = 3,5 cm

Panjang busur
= α/360° × 2πr
= 80°/360° × 2 × 22/7 × 3,5
= 2/9 × 44/7 × 3,5
= 308/63
= 4,888...
= 4,89 cm

Semoga bisa membantu...