Guest: how much boiling water (L) must you add to a luke warm tub (25 degrees Celsius, 1000L) to bring the temperature up to 40 degrees Celsius. I believe that the equation goes something like this: Mass1*Specific Heat Capacity of water*initial temperature= (Mass1+Mass2)(Specific Heat Capacity of water)(Final temperature)
Energy required to raise 1000L of luke warm water from 25degC to 40degC is masslukewarm*spht*(40-25)
The energy supplied by boiling water to go from 100degC to 40degC is masshot*spht*(100-40)
Equating these two and assuming the specific heat is constant over the range of temperatures being considered and that the density is also constant at 1000kg/m
3, and knowing that 1000L is 1m
3 (so masslukewarm = 1m
3*1000kg/m
3 = 1000kg), then
masshot*spht*60=masslukewarm*spht*15
masshot = masslukewarm*15/60
masshot = 1000kg*15/60
masshot = 250kg
+33616 
