The name of this card game can be traumatic for some students. For students who have lived in areas of armed conflict, "war" is not an appropriate name for a light-hearted card game. An alternative name you might consider is "Top-it".
The basic game is easy to learn. Here are the basic rules:
Most of these versions can be played with a regular deck of playing cards. (You could remove the face cards, make all face cards equal 10 or use J=11, Q=12, K=13. Jokers could be removed or have a value of zero. Aces can be either 1 or 11.) If you want to use basic number cards, you can steal them from a UNO deck or any other numerical card game you might have laying about (e.g. Skip-Bo, Zero Down, Krypto, etc). Some might need special cards to be printed off such as (Logarithm War).
Representing Numbers War - A special deck of cards is used showing a variety of ways to represent numbers from one to twenty. Representations might include numerals, tally marks, ten frames, dominoes, dot patterns, fingers, etc.
Place Value War - Students flip two cards (A-9) to make a two digit number (or three cards for a three digit number). They get to choose which represents the tens place and which is the units place. Ask students to read their number out loud, “five tens and three ones equals fifty-three.”
Addition or Subtraction War - Each student flips two cards and either adds or subtracts them to get their value. Ask students to read aloud the number sentence created by their cards. For example, if the student draws a 4 and a 6, they should say, "four plus six equals ten" or "the sum of four and six is ten".
Decimal War - Similar to place value war, each student flips two or more cards to create a decimal number. You could create special deck to include fractions, decimals and percents as well as pictorial representations of rational numbers.
Evaluating Functions War - Students determine the value of a function at two different points to see which is greater. Students get practice evaluating functions from a table, equation, or graph. Sarah Carter has shared a set of cards she created for this activity.
Radians and Degrees War - Practice mentally comparing angle measurements in radians and degrees using a special set of cards. Sarah Carter has a link to a free set and a description of this activity.
Trig War - Play with cards with sine, cosine and tangent trig expressions and special angles on the unit circle (in both radians and degrees). Sam Shah has a link to a set of cards to download and a description of this activity.
Do you use any other versions of War in your classroom? Do you know a great deck of custom cards ready to download? Let me know.