Answer: 
1500 m/s 
Step-by-step explanation: 
The formula for the period T of a wave is 
 T = 1/f Invert each side 
(1) f = 1/T 
The formula relating frequency f and wavelength λ is 
(2) fλ = v Substitute (1) into (2) 
 v = λ/T 
 
Data: 
λ = 9 m; T = 0.006 s 
 
Calculations: 
v = 9/0.006 
v = 1500 m/s