Struggling with a past paper question. DONT WANT ANSWERS JUST A NUDGE

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buzz_benj
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this is the question; it's just blown me a bit as there 3 materials involve the water, container and ball :s

I don't expect answers, nor do i want them, I', just stuck and need a push to gte my head round it, what I've tried so far gave me a final temp of 20.00008 degrees c, guessing that's wrong

A copper container, of mass 0.6 kg, holds 1.5 kg of water at 20°C. An iron ball, of mass 100g and at a temperature of 120°C, is dropped into the water. Assuming no heat transfer to or from the surroundings, estimate the final temperature of the water.
Use the specific heats (kJ/kg K): copper: 0.387, water: 4.2, iron: 0.448
 
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Write an equation for the heat energy gained or lost by each object in terms of the knowns and unknowns. For example you know the initial temperature of the iron ball but not the final temperature. Solve.

There is a reasonable assumption you will have to make that isn't stated in the problem.
 
is it, that the energy in the system remains constant?
 
buzz_benj said:
is it, that the energy in the system remains constant?

That's already stated in the problemwhen it says..

Assuming no heat transfer to or from the surroundings
 
worked it out, I am a moron and buggered up the rearranging of the equation to make the final temp the subject, i think the answer is 20.71