How the beta of a portfolio can equal the market beta if 50 percent of the portfolio is invested in a security that has twice the amount of systematic risk as an average risky security?

The beta of a portfolio is the weighted average of the betas of its individual securities. If 50 percent of the portfolio is invested in a security with a beta of 2 (twice the market's systematic risk), and the other 50 percent is invested in a security with a beta of 0 (no systematic risk), the portfolio's beta can be calculated as follows: (0.5 * 2) + (0.5 * 0) = 1. This means that the portfolio has a beta of 1, equal to the market beta, due to the balancing effect of the low-risk security.