The bakery in my neighborhood sells rolls at 30 cents per unit. It also sells them in packages of 7 rolls at € 1 or in packages of a dozen for € 1.80. My mom gave me a € 10 bill and told me to buy 60 rolls and keep the change. I want to buy at least 60 rolls and keep as much money as possible.
What is the most money I can stay with?
The cheapest rolls are those that are sold 7 in 7. We must buy the maximum possible of this group and complete with those that are sold 12 in 12 which are the next cheapest.
You must buy 7 packages of 7 and a package of 12. Although you buy 61 rolls, it comes cheaper than buying 60 making other combinations. He will keep € 1.20