These three activities help students practice building their mental math skills by becoming aware of how to use benchmark problems to estimate answers for other problems. The OVER and UNDER activity helps students estimate whether a math answer is under or over a certain number. For instance: 50 x 10= 500, so 49x 10 would be less than 500, but 51 x 10 would be over. Students could use their reasoning skills and share their methods with others. This is a great activity to use as a whole group, but can also be used in a math center. Group response cards and student sheets are available.
The two compatible number activities help students quickly add more than two numbers by putting together compatibles, numbers that equal 50 or 100. Answer cards are available. I have used these for early finishers and accelerated students who like the challenge of practicing mental math.