# Water was poured into hot water weighing 3 kg heated to 90 degrees at 15 degrees

Water was poured into hot water weighing 3 kg heated to 90 degrees at 15 degrees, while all the water became 60 degrees. How much cold water was poured.

To calculate the mass of the added cold water, we apply the equality: Cw * mhol * (tу – tсhol) = Cw * mоr * (tор – tу), from where we express: mоrе = mоr * (tор – tу) / (tу – tоr).

Variables: mhot is the mass of hot water (mhot = 3 kg); thot – temperature before mixing hot water (thot = 90 ºС); tу – steady-state temperature (tу = 60 ºС); tcold – temperature before mixing cold water (tcold = 15 ºС).

Let’s make a calculation: mcold = mhor * (thot – tу) / (tу – tcold) = 3 * (90 – 60) / (60 – 15) = 2 kg.

Answer: 2 kg of cold water was added to 3 kg of hot water.

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