$\therefore \mathrm{v}=256 \times 101.6 \mathrm{cm} / \mathrm{s}$
$\mathrm{n}_{2}=\frac{\mathrm{v}}{4 \ell_{2}}=\frac{256 \times 101.6}{4 \times 25.6}=254 \mathrm{Hz}$
No. of $beats/sec$ $=\mathrm{n}_{1}-\mathrm{n}_{2}=256-254=2$
${y_1} = 0.05\,\cos \,\left( {0.50\,\pi x - 100\,\pi t} \right)$
${y_2} = 0.05\,\cos \,\left( {0.46\,\pi x - 92\,\pi t} \right)$
then velocity is..... $m/s$
