If ‘2’ moles of diatomic gas and 1 mole of monoatomic gas are mixed, then the ratio of specific heats for the mixture is

we know CP mix=μ1CP1+μ2CP2μ1+μ2;CV mix=μ1CV1+μ2CV2μ1+μ2;CP =γRγ-1;CV =Rγ-1 γmixture of gases=CP mixCV mix γmixture of gases=μ1γ1γ1−1+μ2γ2γ2−1μ1γ1−1+μ2γ2−1 for monoatomic gas γ=53 ;for diatomic gas γ=75 given μ1=1 and μ2=2 substitute the valus in γmixture of gases  as⇒γmixture of gases=5353−1+14575−1153−1+275−1=1913