Whatever the situation, it's always good to have that quick, go-to activity on hand that is guaranteed to fill that last-minute need.
My secret for keeping my sanity is to change things up. I do this with Crack the Code puzzles! These activities are a fun way for students to practice different math skills and they're each self-correcting. (The last thing I want to do the first week of school is to start grading papers!) Each Crack the Code puzzle takes approximately 40 minutes. If the quote at the bottom doesn't make any sense, then they've made some kind of error in their work and need to go back and find it.
With that in mind, let me share one of my favorite puzzles, Adding & Ordering Decimals (to thousandths)- Crack the Code. This particular activity is a 3-step problem, giving you some good start-up information about their understanding of adding and placing decimals in order from greatest to least. The teaching notes offer some suggestions in differentiating the task, as well as different ways to use it. One of the things I like about this particular puzzle is the "atta girl/boy" encouragement offered from the quote in the book, The Phantom Tollbooth by Norton Juster: "Never feel badly about making mistakes, as long as you take the trouble to learn from them."
And here's the best part (besides the no-grading part, that is, which is pretty sweet, as well): Crack the Code puzzles are extremely low prep - just print the student copy and hand them out!
This puzzle is included in the The Phantom Tollbooth Crack the Code Bundle, a collection of 8 different puzzles, with some of my favorite quotes from that wonderful book. Also included, a poster set of each of the 8 quotes used.