You start with $100 and you arbitrarily start with 10 shares. Each equal to $10 ($100/10 = $10 per share)
you make 50% so
$150/10 =$15 per share
You take out $30
You redeem 2 shares ($30/$15=2 shares)
$120/8 = $15
you make 50% so
$180/8 = $22.50 per share
You take out...