The relative density of Kerosene is $0.8$. Find its density. (in $kg/m^3$)

If a substance of mass $m_1$ and specific gravity $s_1$ is mixed with a substance of mass $m_2$ and specific gravity $s_2$,what is the specific gravity of the mixture?

Pressure at the bottom of a tank of water is $3P$,where $P$ is atmospheric pressure. If water is drawn out till the level of water is lowered by one-fifth,then the pressure at the bottom of the tank is

An open $U$-tube contains mercury. When $13.6 \,cm$ of water is poured into one of the arms of the tube,then the mercury rise in the other arm from its initial level is ....... $cm$

$A$ hollow sphere of radius $R$ is filled completely with an ideal liquid of density $\rho$. The sphere is moving horizontally with an acceleration $2g,$ where $g$ is the acceleration due to gravity. If the minimum pressure of the liquid is $P_0$,then what is the pressure at the centre of the sphere?

When two metals of equal volume are mixed,the relative density of the mixture is $4$. When equal masses of these two metals are mixed,the relative density of the mixture is $3$. What are the relative densities of the two metals?