To find final temperature: ∆Q = mc
100 g of water originally at 90°C will loose an amount of heat,
∆Q = mc ∆T
∆Q = 100 × c × (90 – T)
The same amount of heat will be absorbed by 600g of water originally at 20°C to raise its temperature to T.
∆Q = 600 × c × (T – 30)
600C (T – 20°) = 100C (90° – T)
6T – 120° = 90° – T
6T + T = 120° + 90°
7T = 210°
⇒ T = 210/7
T = 30°C
