Offer your thoughts or opinion on the input financial query or topic using your financial background.

How to allocate profit and loss in partnership where one partner's activities are profitable and the other's aren't? 
You should have a partnership agreement of some sort.  The reason partnership agreements exist is so nobody can change the game because of the outcome.   I'd say the most typical partnership agreement is that everyone gets an equal cut, meaning that everyone also makes an equal contribution.  If you have start up expenses of $10,000, you'd each contribute $5,000.  Separately, you can determine ownership share by contribution amounts, maybe one of you contributed $2,000 and the other $8,000; this would be an 80/20 split. The performance of the operation doesn't have anything to do with determining how to divide the pie, your partnership agreement determines that.  How much have you each contributed and what agreement did you make before you decided to be partners? If you have a poor performing business segment, then the partnership should get together and consider adjusting or stopping that line of business.  But you don't change how the pie is divided because of it; unless your partnership agreement says you do.