A block of solid insoluble in water weighs 24gm in air and 21gm when completely immersed in water. Its weight when completely immersed in liquid of specific gravity 1.1 is                            

Weight of solid in air w₁ = 24g

Weight of solid in water w₂ = 21g

The specific gravity of liquid = 1.1

Weight of solid in liquid w₃ =?

Specific gravity $\frac{{\mathrm{\rho }}_{\mathrm{L}}}{{\mathrm{\rho }}_{\mathrm{W}}}=\frac{{\mathrm{w}}_1-{\mathrm{w}}_3}{{\mathrm{w}}_1-{\mathrm{w}}_2}$ 

$\frac{1.1}{1}=\frac{24-{\text{w}}_3}{24-21}$

$\frac{11}{10}=\frac{24-{\text{w}}_3}{3}$

$24-{\text{w}}_3=3.3$

${\text{w}}_3=24-3.3=20.7\text{gm}$