Calculate the final temperature

[غلامعلی نوری]

you add 2 liters of water with temperature 70° C on 2 liters of water with temperature 40 ° C
Calculate the final temperature now

[m!sS Nah!D]

solution with some details

Heat gained by cold water = Heat lost by hot water
mass X temp ch X heat cap. = mass X temp ch X heat cap.

2 litre of water=2000 g

The "heat cap." are the same and can be cancelled out, leaving us with:
mass X temp ch = mass X temp ch

2000 X (t-70) = 2000 X (40-t)
2000 t - 140,000 = 80,000 - 2,000 t

re-arrange to get:

2000 t+2000 t=80,000+140,000
4000 t=220,000
t=55