To keep things simple, we choose the number of shares closest to a $10,000 investment, rounded to the nearest 10 shares. Thus each trade is roughly equally sized and the percentage gain easy to determine.
For example, if you bought a number of shares totaling a $10,000 investment and then sold those
shares for $10,350, your $350 profit represents a 3.5% gain, not including commissions. Of course, in real-world trading, the number
of shares you trade (if any) is entirely up to you.