Soal mengenai intensitas bunyi

BUNYI
• intensitas

Pa = 1,2 W. rca = __?
Pb = 0,3 W. rcb = __?

intensitas bunyi
I = P / A
I = P / (4π r²)

Ica = Icb
Pa / (4π rca²) = Pb / (4π rcb²)
Pa / rca² = Pb / rcb²
rca² / rcb² = Pa / Pb
(rca / rcb)² = Pa / Pb
(rca / rcb)² = 1,2 / 0,3
(rca / rcb)² = 4
rca / rcb = 2
rca = 2 rcb

yang memenuhi option [C]
(dengan catatan, jarak 12 m boleh berubah)