a sound wave has a frequency of 2KHz and wavelength 35 cm.how long it will take to travel 1.5km?

The speed of the sound wave will be

v = wavelength x frequency

or

v = λ x f

here,

λ = 35cm = 0.35m

f = 2kHz = 2000 Hz

thus,

v = 0.35 x 2000 = 700 m/s

now, time taken by it to travel 1.5km (=1500 m) will be

t = velocity / distance = 700/1500

thus,

t = 0.467 seconds