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Long(100%)-Short(-100%) investment explanation
There is no difference.  When dealing with short positions, talking about percentages become very tricky since they no longer add up to 100%.  What does the 50% in your example mean?  Unless there's some base amount (like total amount of the portfolio, then the percentages are meaningless.  What matters when dealing with long and short positions is the net total - meaning if you are long 100 shares on one stock trade and short 50 shares on another, then you are net long 50 shares.