Mining computations by the numbers On average, how many "computations" (GPU computations, CPU computations, CPU cycles, etc.) does it take to solve a block ("win" a mining race)?

What are these computations measured in? Operations? Operations per second? Something else? Thanks in advance!
When mining, you computer creates hashes. These hashes must satisfy a certain condition. All a miner does is trying many many times to find a valid hash for a block.

For this reason, mining hardware performance is measured in GH/s, giga-hash-per-second, which are one billion hash calculations per second and it is called the hashrate.

It is good to know that there is no fixed amount if hashes required to find a valid hash. The Bitcoin network has a dynamic difficulty for the mining problem. This difficulty is used to make sure new bitcoins are generated at a predictable rate. The difficulty is changed every 2016 blocks, and is adapted so that it will take as close as possible to 2 weeks for the next 2016 blocks. This means that, at average, every 10 minutes a new block is found.

The chance of finding a good hash within such 2 weeks is fixed. This means that you can find one after only a few tries or it can take you weeks or even months to find one. When the total hashrate of the network raises, 2016 blocks will be found in less than 2 weeks. In this case the difficulty will automatically be adapted so that the next 2016 blocks will take 2 weeks, considering the recent hashrate change.