Two identical flutes produce fundamental notes of frequency 300 Hz at 270C. If the temperature of air in one flute is increased to 310C, the number of the beats heard per second will be

Velocity of sound increases if the temperature increases. So with v=nλ, if v increases n will increase  at  27oC,  v1=nλ, at  31oC ,   v2=(n+x)λNow using v∝T           ∵v=γRTMv2v1=T2T1=n+xn⇒300+x300=(273+31)(273+27)=304300=300+4300⇒1+x300=1+43001/2=1+12×4300  ⇒x=2                                                    [∵( 1+x)n=1+nx]