A piece of metal weight 45 g is air and 25 g in a liquid of density `1.5 xx 10^(3)kg-m^(-3)` Kept at `30^(@)`. When the temperature of the liquid is raised to `40^(@)C`, the metal piece weight 27g. The density of liquid at `40^(@)C` is `1.25 xx 10^(3) kg-m^(-3)`. The coefficient of linear expansion of metal is