Heavy science Question?

[Lazy-Ferret]

My wife and I had an interesting conversation this morning, to which neither of us know the answer. I thought a quick look on Google would answer it, but I can't find it on there either...

So here is the question...

Assuming there are no outside losses, the room is thermostatically set at 20c.

I have 2 identical jugs of water each with exactly 1 litre of water in, but one is at 30c, and one is at 10c.

if both jugs are left in the room, which will get to 20c first, the hot or cold one?

Also, along the same lines, if I had 1/2litre at 90c, and poured 1/2litre of 10c water into it, what would be the end temp of the 1litre.

To me, these should be a fairly easy way to work this out, but I can't find it anywhere.