The relative humidity on a day, when partial pressure of water vapour is $0.012\times {10}^5 \mathrm{Pa}\text{ at }12°\mathrm{C}$ is ___? ( vapour pressure of water at$12°\mathrm{C}\text{ is }0.016\times {10}^5 \mathrm{Pa}\text{ ) }$

Partial pressure of water vapour,

$P_w=0.012\times {10}^{5}Pa$

$\text{ Vapour pressure of water }\mathrm{P}=0.016\times {10}^5 \mathrm{Pa}$

The relative humidity at a given temperature is given by,

$=\frac{\text{ Partial pressureof water vapour }}{\text{ Vapour pressureof water }}=\frac{0.012\times {10}^5}{0.016\times {10}^5}=0.75\text{ or }75\%$