Help Needed: Solving Tf in Metal & Liquid Heat Exchange

[tedjj]

I can't solve this problem. Could anyone help me?
A piece of metal with a mass of 2kg and specific heat of 200J/kg C is initially at a temperature of 120 C. The metal is placed into an insulated container that contains a liquid of mass 4kg, a specific heat of 600J/kg C, and an initial temperature of 20C.
I am using equation
Mm * Cm(Tf-Ti)=Ml*Cl(Tf-Ti)
2*200*(Tf-120)=4*600*(Tf-20)
(Tf-120)=6*(Tf-20)
Tf-120 = 6Tf-120
Tf=6Tf
Where did I make a mistake?
Thanks

 

[da_willem]

In the first formula you use there should be a minus sign on one of the sides. This is an energy equation; energy is conserved so the amount of heat that the metal loses (-) is gained (+) by the liquid...

 

[tedjj]

ohh You are right. Thank you very much.