If you were to get multiple miners that do 7.3TH/s do they add up. for example if i had 3 of them would it give me 21.9TH/s? Also What is the coversion rate for TH like how much is 1TH worth in usd?
Possible duplicate:- Does mining power of different miners add up in mining pools?
Mining is a lottery, not a race.
The fastest miner doesn't always win. In general, if you have X% of the hashrate, you will find X% of the blocks.
This is because not just all pools, but every every, every chip, ... is attempting to solve a different block proposal. Every attempt has an independent chance of winning. There are an infinite number of potentially valid blocks, but they're still only a tiny fraction of all possible blocks. Everyone is not trying to find the next block - they're trying to find a next block.
Can I add up my hashpower and make it work like a single processor of 1000H/s
Yes. You can't distinguish the different processors - more hashpower just tries more block proposals at the same time.
Both both miners would be acting independently?
Yes. Everything always acts independently.
So this means a mining pool has combined power of all the associated miners and working on one block?
All miner are working on different block of their own ??