I use this 4 day mini unit to start off the year and it never disappoints students. You are using math in a real life application and its not boring. Students will need to use all four operations & discuss divisibility. The four lessons include UPC(universal product code) numbers, ISBN (international standard book number) numbers, validating credit card numbers and working with VIN (vehicle identification numbers). There are a variety of questions that differentiate from easy to harder in the same assignment. I love teaching this unit and you will too! There are also videos and more practice problems that I will email you if you purchase this product.