Question

find the speed of sound (in m/s) at -35°C at 1 atm pressure in dry air

Answer 1

There are many websites online provide the speed of sound in air as a function of temperature.

Try this one:
http://www.sengpielaudio.com/calculator-speedsound.htm

The most accurate formula is
Speed of sound = sqrt[(gamma)*R*T]
where T is the Kelvin temperatuere and gamma is the specific heat ratio, which is 1.4 for dry air. R' is the molar gas constant divided by the molecular weight of air .

Answer 2

thank you!