This PRINTABLE set of 48 cards allows students to strengthen their mental math skills by determining what the missing number is. It is a subatizing lesson with a twist. Students see one group of objects and a number. They must recognize the number in the group of objects and then figure out what number is missing to equal the total. Critical thinking skills are used and it's great practice for kids to sharpen their ability to problem solve in their heads. Colorful, bright, cheery cards. Numbers go from 4 - 17. Most cards are in the 7 - 12 range. Really helps with speed with facts. I suggest printing on card stock and they can be used all year.