What temperature will the water have if you mix 20 liters of hot at 80 degrees and 10 liters of cold at 20 degrees?

Vg = 20 l = 0.02 m ^ 3.
tg = 80.
Vx = 10 l = 0.01 m ^ 3.
tx = 20.
t -?
When mixed, hot water will give cold water a certain amount of heat Q and its temperature will drop to t.
This amount of heat is determined by the formula: Q = c * mg * (tg – t), where c is the specific heat capacity of water, mg is the mass of hot water, tg is the initial temperature of hot water, t is the water temperature after mixing.
Cold water will receive the amount of heat Q, which will give up hot water and heat up to a certain temperature t.
The amount of heat that will go to heat cold water is determined by the formula: Q = c * mх * (t – tх), where c is the specific heat capacity of water, mх is the mass of cold water, tх is the initial temperature of cold water, t is the water temperature after mixing …
mg = Vg * ρ, mх = Vх * ρ, where ρ is the density of water.
c * mg * (tg – t) = c * mx * (t – tx).
c * Vg * ρ * (tg – t) = c * Vх * ρ ​​* (t – tх).
Vg * (tg – t) = Vx * (t – tx).
Vg * tg – Vg * t = Vx * t – Vx * tx.
Vg * tg + Vx * tx = Vg * t + Vx * t.
Vg * tg + Vx * tx = (Vg + Vx) * t.
t = (Vg * tg + Vx * tx) / (Vg + Vx).
t = (0.02 m ^ 3 * 80 + 0.01 m ^ 3 * 20) / (0.02 m ^ 3 + 0.01 m ^ 3) = 60.
Answer: after mixing, the water temperature will be t = 60.