This activity goes along with the standard 2.NBT.b.8 and would be a perfect game to use during math centers to allow students to work together and have fun while learning!
I color coded each card set.
Blue = 3 digit +10 and +100
Red = 3 digit -10 and -100
The yellow and orange cards are all two digit numbers +/-10 or +100. These are a way to differentiate with those students not quite ready to work with three digits mentally.
Basically, one student will work with a calculator, and the other student is working to solve the cards mentally. The person doing it mentally wants to get the correct answer faster than the person with the calculator.