The reserve requirement ratio does not do what you think it does. It is the amount of money that the bank is required to keep in its account at a Federal Reserve Bank as a ratio of deposits. Note that literal cash sitting in a vault does not count one iota towards satisfying this reserve ratio.

Bank regulations have moved one from having such a specific requirement. Nowadays, you essentially need a minimum amount of equity per risk-weighted assets. So you need something like $8 in cash for every $100 in loans you give out.