Al calorimeter (0.1 kg, c=900) with 0.2 kg water at 20°C. 0.3 kg metal at 100°C added. Final T=25°C. Find c of metal.

Heat lost = 0.3×c×(100-25)=22.5c. Heat gained = water: 0.2×4200×5=4200 J, calorimeter: 0.1×900×5=450 J, total=4650 J. 22.5c=4650 → c=206.7 J/kg°C.…