The ratio of sp to sp² carbons in $\mathrm{HC}\equiv \mathrm{C}-\mathrm{CH}={\mathrm{CH}}_2$ is --------------

[Step 1]:
Double bonded carbon is sp2 hybridized and triple bonded carbon is sp hybridized
[Step 2]:
 $\underset{\mathrm{SP}}{\mathrm{HC}}\equiv \underset{\mathrm{SP}}{\mathrm{C}}-\underset{{\mathrm{SP}}^2}{\mathrm{CH}}=\underset{{\mathrm{SP}}^2}{{\mathrm{CH}}_2}$
[Step 3]:
Number of SP hybridized carbons are two .Number of SP2 hybridized carbons are two
[Step 4]:
Therefore the ratio of SP carbons to SP2 carbons is $\frac{2}{2}$i.e one.