You are thinking about it wrong.

Don't think of your organization as a pie. Think of it as a house.

When you add an extension (say a new kitchen) to your house, the value of your new kitchen now accounts for a larger *percentage* of your house, more than it did before.

But something else also happens. Your house is now worth a lot more.

I highly recommend you watch the series on raising money for a startup by the Khan Academy - http://robt.co/1u1wCsx