How much cold water with a temperature of 10 ° needs to be added to cool 2.5 liters

How much cold water with a temperature of 10 ° needs to be added to cool 2.5 liters of water taken at a temperature of 90 ° to a temperature of 50 °?

Task data: t1 (cold water temperature) = 10 ºС; V2 (hot water volume) = 2.5 l; t2 (hot water temperature) = 90 ºС; t3 (temperature to which hot water will cool down) = 50 ºС.

Let’s draw up equality and calculate the amount of cold water:

C * m1 * (t3 – t1) = C * m2 * (t2 – t3).

С * ρ * V1 * (t3 – t1) = C * ρ * V2 * (t2 – t3).

V1 * (t3 – t1) = V2 * (t2 – t3).

V1 = V2 * (t2 – t3) / (t3 – t1) = 2.5 * (90 – 50) / (50 – 10) = 2.5 * 40/40 = 2.5 liters.

Answer: You will need to add 2.5 liters of cold water.