20 Sum Challenge was our 10 minute-ish warm up for maths every day. The kids would get themselves set ready to go, I'd set the timer and the kids would do 1 row. As soon as they were finished they'd stand up and say 'done!' I'd read them out a time which they'd record. Early finishers would read quietly 'til everyone finished, but we'd never go past 10 minutes (sometimes 5 minutes). Then we'd switch books and correct. The students would record their accuracy rate and their times on the second sheet (many kids had difficulty doing this so myself or the teacher aide would do it.) We'd make a bar graph of our accuracy rates and a line graph of our times. The kids got a real kick out of seeing their progress. I didn't give them the whole 24 pages at once, just 4 pages of sums plus the cover and the results sheet.
20 Sum Challenge Number Facts (24 page word doc)