Ratio of ‘sp³’  hybrid orbitals to ‘sp²’  hybrid orbitals in But-2-ene is

.$\underset{\mathrm{But}-2-\mathrm{ene}}{\stackrel{{\mathrm{sp}}^3}{\mathrm{C}}{\mathrm{H}}_3-\stackrel{{\mathrm{sp}}^2}{\mathrm{C}}\mathrm{H}=\stackrel{{\mathrm{sp}}^2}{\mathrm{C}}\mathrm{H}-\stackrel{{\mathrm{sp}}^3}{\mathrm{C}}{\mathrm{H}}_3 ;}$

Number of ‘sp³’ hybrid orbitals = 2$\times$4 = 8 ;

Number of ‘sp²’ hybrid orbitals = 2$\times$3 = 6 ;

Ratio of ‘sp³’  to ‘sp²’ hybrid orbitals = 8 : 6 = 4 : 3 ;