The ratio of SP to SP² carbons $\mathrm{HC}\equiv \mathrm{C}-\mathrm{CH}={\mathrm{CH}}_2$ in  is --------------

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.