Subtraction

Subtraction war You need: playing cards (Q for zero, all other face cards removed), mini-whiteboard and markers

From 20
Each player pulls out one playing card. Both players subtract their number from 20 and writes the answer on their whiteboard. The smallest number on the mini-whiteboard wins all the cards from the round. Erase whiteboard and play again. Count the captured cards at the end of the allocated time, or shuffle captured cards and keep going until one player has all the cards.

Up to 100
Same as above except each player pulls out three playing cards. Each player decides two of them to make into a 2-digit number, then subtract the third. Example: Suppose you pull out 3,4, and 5. Should you arrange them as 54-3 or 45-3 or 35-4 or. . . ?

From 100
Same as above except each player pulls out two playing cards - one card represents the tens, the other represents units Both players subtract their number from 100 and writes the answer on their whiteboard

Beyond 100
Same as up to 100 but each player pulls out five playing cards and make a 2-digit number to subtract from a 3-digit number.

First to Zero
This game can be played with counters for those students who need the concrete materials, otherwise whiteboards are great. The beginning number is 21. Students take turns at subtracting 1, 2 or 3 in turn. The winner is the student who ends up on ZERO.

See if students can determine a strategy to ensure they win every game?