Use this as a center or a whole class activity with iPads, iPods, etc.! Students practice their place value skills by completing problems and self-checking their answers. The students complete a problem and then scan the QR code to see the correct answer. Students can work in pairs or individually for this activity. I worked with all of our 3rd grade classes on this, and the kids loved it! We used a free app called i-Nigma to scan our QR codes. Included in this download are my guidelines for iPad use, instructions, 12 math problems, and QR codes.