I assume the definition of raising money is that the original owner gives some percentage of the company to a new owner, and the new owner gives an amount of money to the company.
Let's say the company's valuation is 1 million dollars. Let's say the owner sells 10% for 0.1 million dollars.
In a perfect market the company's new valuation is obviously 1.1 million dollars: the original value in the company's resources (people, etc...) plus the 0.1 million in the bank.
On the other hand in a perfect market perfect owners made a deal in which the original owner's wealth is the same before and after the deal.
Before the deal he was worth 1million. After the deal he is worth 0.9*x, where x is the new valuation of the company.
So:
1million dollars = 0.9x
x = 1.1111' million dollars
So which is the correct new valuation: 1.1, or 1.1111'? Or something different?
Maybe the deal have to be made in infinitely small pieces, so the result is coming from some kind of differential equation?