When you take a bath, how many kilograms of hot water (40.8 °C) must you mix with cold water (11.3 °C) so that the temperature of the bath is 30.9 °C? The total mass of water (hot plus cold) is 190 kg. Ignore any heat flow between the water and its external surroundings.

1 answer

Q₁=m₁cΔT₁
Q₂=m₂cΔT₂
m₁cΔT₁=m₂cΔT₂
m₁ΔT₁=m₂ΔT₂
m₁ΔT₁=m₂ΔT₂
m (40.8 -30.9)=(190-m)(30.9-11.3)
Solve for ‘m’