Jawabanmu

2014-04-03T21:05:56+07:00
PA = 3PB
fA = 30 Hz
PA = 1/fA
PA = 3PB maka 1/30 = 3PB
PB = 1/30 : 3 = 1/30 x 1/3 = 1/90
fB = 1/PB
fB = 1/1/90 = 90Hz
2014-04-03T21:07:00+07:00
Periode getaran A:  \frac{1}{30}  
periode getaran B:  \frac{1}{30} ÷ \frac{1}{3}
                        ⇒  \frac{1}{90}
maka, frekuensi getaran B:  \frac{1}{ \frac{1}{90} } = 90 Hz
whoops. maksudnya 1/30 x 1/3. Maaf, aku belum mengerti cara memakainya ^^;
makasih ya :)