Find the ratio of ${\mathrm{sp}}^2$ and ${\mathrm{sp}}^3$ hybridized boron atoms in ${\mathrm{Na}}_2{\mathrm{B}}_4{\mathrm{O}}_7·10{\mathrm{H}}_2\mathrm{O}$.

Structure of borax is:

Two boron atoms that are negatively charged have sp³ hybridization and rest of two boron atoms have sp² hybridization. Therefore the ratio of sp² and sp³ hybridized boron atoms is 2:2 or 1:1.