${\mathrm{\lambda }}_{\mathrm{e}}={\mathrm{\lambda }}_{\mathrm{n}}$

$\frac{\mathrm{h}}{{\mathrm{m}}_{\mathrm{e}}.{\mathrm{v}}_{\mathrm{e}}}=\frac{\mathrm{h}}{{\mathrm{m}}_{\mathrm{n}}.{\mathrm{v}}_{\mathrm{n}}}$

${\mathrm{\lambda }}_{\mathrm{e}}=$Wavelength of electron

${\mathrm{\lambda }}_{\mathrm{n}}=$Wave length of neutron

${\mathrm{m}}_{\mathrm{e}} \mathrm{and} {\mathrm{M}}_{\mathrm{n}}=$Mass of electron and neutron respectively

${\mathrm{v}}_{\mathrm{e}} \mathrm{and} {\mathrm{v}}_{\mathrm{n}}=$Velocity of electron and neutron respectively

$\mathrm{h}=6.626\times {10}^{-34}\mathrm{Js}=$Planck's constant

${\mathrm{m}}_{\mathrm{e}}.\mathrm{x}.{\mathrm{v}}_{\mathrm{n}}={\mathrm{m}}_{\mathrm{n}}.{\mathrm{v}}_{\mathrm{n}}$

$\mathrm{x}=\frac{{\mathrm{m}}_{\mathrm{n}}}{{\mathrm{m}}_{\mathrm{e}}}=\frac{1.6\times {10}^{-27}}{9.1\times {10}^{-31}}$

$\Rightarrow \mathrm{x}=\frac{16}{9}\times {10}^3$

$=1.758\times {10}^3$

$=1758$