1/2=2/4 so you do 2/4+3/4=5/4
You have to make sure you do the same number for the denominator
Australia is an island country, and besides the big main island and Tasmania, it has 12,000 islands plus in its territory. Since it doesn't have any land borders, its borderline is actually the sum of all coastlines of all islands in its territory, and that accounts for 70,000 km.
New South Wales is the biggest state in the country, and it occupies 10% of its total land mass. Its border is 4,635 km, which means that it accounts for 6.62% of the total borderline of Australia.
