tolong dijawab ya kak....nomor 13&15 Besok dikumpul

13.) Waktu/Time (t) = 0,25 s
Panjang/Wavelength (λ) = 30/1,5 = 20 cm
Jumlah/Number (n) = 1

Frekuensi/Frequency (f):
f = n/t
f = 1/0,25
f = 4 Hz

Cepat rambat/Velocity (v):
v = λ.f
v = 20.4
v = 80 cm/s ⇐ Jawaban D ✓

15.) Waktu/Time (t) = 0,25 s
Jumlah/Number (n) = 2,5
Panjang/Wavelength (λ) = 50/2,5 = 20 cm

Periode/Term (T):
T = t/n
T = 0,25/2,5
T = 0,1 s ⇐ Jawaban B

Cepat rambat/Velocity (v):
v = λ/T
v = 20/0,1
v = 200 cm/s ⇐ Jawaban B