Wikipedia:Reference desk/Archives/Computing/2018 May 27

= May 27 =

How can I accomplish this in Microsoft Excel 2016? Operating with values of time.
How can I accomplish this in Microsoft Excel 2016? This question concerns the proper operating with (and formatting of) time in Excel. Let's say that in Cell Number A1, I have a value of time. And in Cell Number B1, I want to specify a certain amount of time to add to (or subtract from) that initial time. And, in Cell Number C1, I want the resulting value. This is somewhat confusing (to me), since I am using the word "time" liberally, whereas I assume that Excel is much more precise. So, to clarify with an example:


 * Cell Number A1: I input the time of day. (Example: 11:52 AM)


 * Cell Number B1: I input the number of minutes that I want to add or subtract.  (Example: 27 minutes)


 * Cell Number C1: I want a formula that gives the correct result.  (In this example:  12:19 PM)

So, how exactly would I format each Cell? And what exactly would I have to type into each Cell?

The Excel functions of "time" are very confusing to me, for many reasons (e.g., the way that Excel considers time, processes time, labels time, etc.) Very confusing. Hence, my questions.

And, again, I understand that in Cell Number A1 and Cell Number B1, I am using the same word, "time", even though I am referring to completely different concepts. That is: Cell Number A1 means "time of day", while Cell Number B1 means "number of minutes".

Thanks! Joseph A. Spadaro (talk) 16:26, 27 May 2018 (UTC)


 * In A1 enter 11:52:00. In B1 enter 00:27:00 (zero hours, 27 minutes, zero seconds).  In C1 enter = A1+B1.  Simples.--Phil Holmes (talk) 17:27, 27 May 2018 (UTC)


 * Thanks. But, that doesn't seem to quite work (to do what I want).  Maybe my question was not clear.  So, let me ask some follow-up questions. I want my "output" to look like this:


 * Cell Number A1: 11:52 AM


 * Cell Number B1: 27


 * Cell Number C1: 12:19 PM


 * Is there a way to get that output?  What I end up getting are values that looks like this:


 * Cell Number A1: 11:52:00


 * Cell Number B1: 00:27:00


 * Cell Number C1: 12:19:00


 * Also, is there an easier way for me to enter the input, without having to type all of those leading and trailing "zeros" and such?   Thanks. Joseph A. Spadaro (talk) 15:37, 28 May 2018 (UTC)


 * Also, what about the "subtraction" of minutes? I cannot get that to work, either.  Thanks.   Joseph A. Spadaro (talk) 16:01, 28 May 2018 (UTC)


 * What do you want to happen if the result is past the end of the day? For example, if you add 30 minutes to 11:45 PM?  I would have thought both A1 and C1 would be date+time but you've only specified time, so the result is not guaranteed to be a valid time. CodeTalker (talk) 18:08, 27 May 2018 (UTC)


 * Thanks. I don't care about the day or date.  Just the time itself.  See my comments above.  That shows the output that I am seeking.  Thanks. Joseph A. Spadaro (talk) 15:37, 28 May 2018 (UTC)
 * Using "Format Cells" you should format A1 as "h:mm AM/PM", format B1 as hh:mm and C1 as "h:mm AM/PM". You need to type in A1 as 11:52, B1 as 00:27 and C1 is calculated. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 00:43, 29 May 2018 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 04:39, 31 May 2018 (UTC)

Economics of Bitcoin Mining
As I understand it, it has become more difficult to make money through mining Bitcoin, both because the rewards (as measured in Bitcoin) are lower and because the blockchains have become longer. This article indicates that the cost to mine a Bitcoin in the United States is $4,758, although the cost is lower in some other countries.

If the Bitcoin rewards for mining fell below the marginal cost of mining (which I assume is lower than the figure in the MarketWatch article), does that mean that the necessary blockchain validation would not be carried out, with potentially catastrophic implications for the viability of Bitcoin? To what extent would this concern be addressed by reductions in the cost of mining, as fewer people choose to engage in mining? John M Baker (talk) 23:32, 27 May 2018 (UTC)


 * To simplify (so don't get anal about details that don't matter)... To mine a bitcoin, you have a computer solve a math problem. The problems are currently very hard to solve. The reason is that there are too many people mining bitcoins. When a bitcoin is successfully mined, the time to mine it is calculated. If it was solved too quickly, the next problem is harder to make it take longer. If it took too long to solve, the next problem will be easier to make it solve quicker. So, if it becomes unprofitable to mine bitcoins, less people will mine them. It will take longer to solve the problem. The next problem will be easier, meaning it will take less resources to mine and therefore be cheaper to mine. So, people will start mining again. 71.85.51.150 (talk) 00:11, 28 May 2018 (UTC)


 * What is the mechanism for adjusting the difficulty of the math problems? John M Baker (talk) 00:52, 28 May 2018 (UTC)
 * Bitcoin seems reasonably clear, and the refs probably contain a more detailed answer. Tigraan Click here to contact me 09:18, 28 May 2018 (UTC)

The bitcoin blockchain is large, about 130 GB today and may reach 1.5 - 1.6 TB in Jan. 2021. However a bitcoin miner does not need to store the whole blockchain (though he may do so as a "full node") because it is a collective function of the bitcoin network to keep all parts of the chain accessible on demand. A short or long blockchain hardly affects the miner's proof-of-work task which is essentially to provide 32 bits of a 640-bit message that can demonstrate a SHA-256 hash-of-hash value below a threshold set (to adjust difficulty) by the network. Corrected "hash-of-hash". DroneB (talk) 12:57, 31 May 2018 (UTC)
 * Thanks to those who responded, and particularly DroneB. John M Baker (talk) 14:54, 30 May 2018 (UTC)