In one metre long open pipe what is the harmonic of resonance obtained with a tuning fork of frequency 480 Hz

In case of open pipe, $\mathrm{n}=\frac{\mathrm{Nv}}{2\mathrm{l}}$ where N = order of harmonics = order of mode of vibration 

$\Rightarrow \mathrm{N}=\frac{\mathrm{n}\times 2\mathrm{l}}{\mathrm{v}}$
$=\frac{480}{330}\times 2\times 1=3$               (Here  v = 330 m/s)