Cold 5’C water weighing 2 kg was poured into hot 70’C water weighing 5 kg. Find the final temperature.

To determine the value of the steady-state (final) temperature, we use the equality: Cw * mhot * (tb – tc) = Cw * mcold * (tу – tcold) and mhp * (tbp – tу) = mcr * (tу – tcold).

Variables: mhot is the mass of hot water (mhot = 5 kg); thot – hot water temperature (thot = 70 ºС); mcold is the mass of cold water (mchol = 2 kg); tcold – cold water temperature (tcold = 5 ºС).

Calculation: 5 * (70 – tу) = 2 * (tу – 5).

350 – 5tу = 2tу – 10.

7tу = 360 and tу = 360/7 = 51.43 ºС.

Answer: After mixing 5 kg of hot water and 2 kg of cold water, a temperature of 51.43 ºС was established.