Vanguard exchange-traded funds (ETFs) are a fantastic choice for retired investors looking to play the long game with their portfolios. Undoubtedly, Vanguard is a name that passive investors can put their trust in.

With volatility spiking and stock market indexes like the S&P 500 (SNPINDEX: ^GSPC) and Nasdaq Composite (NASDAQINDEX: ^IXIC) down on the year, investors may be looking for ways to diversify their portfolios and collect some passive income.

A good example of this comes from some simple math around Schwab U.S. Dividend Equity ETF (NYSEMKT: SCHD), starting with just a $500 investment. What does Schwab U.S. Dividend Equity ETF do? Before getting into the math,