2kg of ice at −20∘C is mixed with 5kg of water at 20o C . The water content of final mixture is (Latent heat of ice = 80 kcal/kg, specific heat of water =1k cal kg−1∘C−1specific heat of ice =0.5k cal kg−1∘C−1)

Heat lost by water=ms θ, heat gained by ice =MS θ+M'L maximum heat loss by water=5×20×1kcal=100kcal heat gained by ice to reach 00C=2×20×0.5=20 kcal  remaining  heat 100-20=80Kcal it is just enough to melt 1 kg of ice. so total water in the mixture=5+1=6kg