# Problem of the Week Problem C Coin Collection

Arya has never travelled to another country, but has a collection of foreign coins given to him by friends and family who have. In his collection he has $$10$$ coins from Africa, $$6$$ coins from Asia, $$7$$ coins from South America, and $$8$$ coins from Europe.

One day Arya’s grandfather added some Australian coins to the collection. After he did that, he told Arya that if he took a coin at random from the collection, the probability of it being from either Africa or Asia was $$\frac{4}{9}$$.

How many Australian coins did Arya’s grandfather add to the collection?

Theme(s): Data Management