Say I had 1 Bitcoin at the start of the trade yesterday

 @ 01-27 14:29

and the price was

 USD : 263.95872470902

So, I sold the whole Bitcoin at the average price


 @ 01-29 10:57

I bought back as much Bitcoin as the new price would let me again at the average price of

 USD : 233.55771464647

The price data was taken from crypto-prices.com I just don't see how that could be worked out. I know how to use preev.com to calculate the 'current' value but I don't understand how I would calculate a previous value and work out the difference / or would be, pretend profit.

  • 1
    I'm voting to close this question as off-topic because this question is essentially about elementary math and as such not a good fit for a Bitcoin experts' question and answer site.
    – Murch
    Jan 29 '15 at 22:51

263.95 [USD/BTC] / 233.56 [USD/BTC] * 1 [BTC] = 1.13 [BTC], i.e. for each BTC you sold at the higher price, you can rebuy 1.13 BTC at the lower price.

The underlying concept is explained on Wikipedia: Cross-multiplication.

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