in my school of faith fixed interest is HARAM.
variable loss & profit based on documented investment are also dubious but under shariah based policies it is legally fine.
without any written documentation formulation for business partnership in profit & loss is highly doubtful.
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what is formulation to calculate profit ?
such formulations are discussed and documented between 2 parties concern, also highly variable based on nature of business / investments.
suna hai / bataya hai / koi keh raha tha it is pure lethargy specially when it is about business investment.
do some effort walk into any local bank and ask for investment schemes. not a tough task isn't it?
is it your earned money or from heirship pot or received in dowry by wedding ??