Bath

There are 30 liters of hot water in the bath. Then we added 39 liters of cold water at a temperature of 19 °C and decreased the temperature of the water to 45 °C.

What was the initial temperature of the hot water?

Final Answer:

T =  78.8 °C

Step-by-step explanation:

$$\begin{gathered} V_1=30\text{l} \\ {V}_2=39\text{l} \\ {V}_1\cdot T+V_2\cdot 19=(V_1+V_2)\cdot 45 \\ 30\cdot T+39\cdot 19=(30+39)\cdot 45 \\ 30T=2364 \\ T=\frac{2364}{30}=78.8 \\ T=\frac{394}{5}=78.8=78.8\text{°C} \end{gathered}$$

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