These strategy based timed tests and posters will help your students to solve addition and subtraction problems with these 40 second assessments. Students are asked to find the sneaky fact that doesn't follow the same strategy to help them learn to identify and use good strategies.This includes many strategies plus individual number timed tests 0-10. Help your students meet the common core math standard 2.OA.B.2 Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers.