The height of a mercury barometer is 75 cm at sea level and 50 cm at the top of a hill. Ratio of density of mercury to that of air is 104. The height of the hill is

Difference of pressure between sea level and the top of hillΔP=h1−h2×ρHg×g=(75−50)×10−2×ρHg×g ………..(i)and pressure difference due to h meter of air  ΔP=h×ρair ×g  ………..(ii)By equating (i) and (ii) we get h×ρair ×g=(75−50)×10−2×ρHg×g∴h=25×10−2ρHgρair =25×10−2×104=2500m∵ρhg= 13600kg/m3 &  ρair= 1.26kg/m3∴Height of the hill = 2.5 km.