Diketahui luas suatu lingkaran 1385,74cm². Jika Phi = 22/7,maka keliling lingkaran tersebut adalah.....

Penyelesaian:
Diket.:
L = 1385,74 cm²
π = 22/7
Ditanya:
K = ....?
Jawab:
πr² = L
22/7 × r² = 1385,74
r² = 1385,74 : 22/7
r² = 1385,74 × 7/22
r² = 9700,18/22
r² = 440,917....
r² = 440,91
r = √440,91
r = √44091/√100
r = √9×4899/10
r = 3√4899/10
r = 3/10 √4899 cm

K = 2πr
K = 2 × 22/7 × 3/10 √4899
K = 132/70 √4899
K = 1 62/70 √4899
K = 1 31/35 √4899 cm

Semoga bisa membantu...