Question 4
At the weekend, Hiền and her sister play shops with homemade money. Instead of writing amounts on blank paper, they use colourful number stickers. Hiền finds four stickers showing 1,3,4 and 5. Placing 1 before 3 makes a 13-đồng note, as illustrated. How should she place these stickers on two pieces of paper to obtain the greatest total amount, using at most two digits on each note?
