If coefficient of cubical expansion is x times coefficient of superficial expansion, then the value of ‘x’ is

coefficient of cubical expansion is γ=xβ here β is coefficient of superficial expansion  γ=3α---(1) but β=2α ⇒α=β2 substitute this value in eqn(1) γ=3β2  given γ=xβ ⇒x=32=1.5