tolong beserta caranya

Diket :
n = 3
t = 0,3 s
λ = 40 cm

Dit :
V = ......?

Jawab:
f = n/t
= 3/0,3
= 10 hz

V =  λ × f
= 40 × 10
= 400 cm/s

nb: Jawabannya ga ada di situ