How can a portfolio have a beta equal to the market beta if $50$ percent of the portfolio is invested in a security with twice the systematic risk of an average risky security?

The beta of the portfolio is the average of the betas of the indmidual securities$,$ and in this case, it balances out to $1\mathrm{.}0$

A portfolio with $50$ percent irmested in a security with a beta of $2\mathrm{.}0$ and $50$ percent in risk$-$free securities foeta of of results in a portfolio beta of $1\mathrm{.}0$

The risk$-$free securities in the portfolio neutralize the risk of the high$-$beta security, resulting in a market beta

The portfolio's beta is calculated using the standard deviation of its components, not the individual betas