All interim dividends must be appropriately annualized before adding up with the year-end final dividends in order to determine the true dollar value of yearly dividends received by the shareholders. For companies that have paid interim dividends, assume that those dividends were paid at the end of the first half of the year and therefore earn six months of interest at a risk-free rate for the next half. The current Australian Government 15-year bonds rate is 1.13% p.a.

Can somebody please explain to me how to annualise the interim dividends where the interim dividend is paid every 6 months, and then add to the final dividend?

E.g. Interim dividend is 17.50 and six months later the final dividend is paid which is 18.50

What is correct answer in this example, and how do you calculate it please?