This is a 21 PowerPoint slide file (w/answer key at the bottom of each slide when not in slideshow format). Answers also pop up when clicked via custom animation w/sound. This is very rigorous and requires sustained thinking in order to solve each problem. I use the PowerPoint file during whole group instruction to the class as a "bell ringer". The format of this is very similar in nature to statewide assessments that are designed to challenge kids. These types of problems need to be done daily so kids can feel more comfortable when having to rise to the occasion of higher order thinking.