A viewer recently sent me a portfolio with nearly 20 ETFs and mutual funds. She didn't create it. An advisor from a major bank recommended it. Ridiculous.The truth is that the number of mutual funds you own tells you nothing about how well diversified the portfolio is or what types of investments you have. A single mutual fund can give an investor exposure to U.S. stocks, bonds, international stocks, REITs, and even commodities. The fewer mutual funds you have, the easier it is to understand and manage your portfolio. This becomes really important when you go to rebalance your investments. It's also critical as you head into retirement and start making withdrawals from you investments each year.In this video, I explain why for the vast majority of investors, all you need is 3 funds.