NIM: A Simple Counting Game to Teach Subtraction Skills

Nim is a traditional, simple, quick, and fun combinatorial game using a stack of counters. Nim looks deceptively easy, but it exercises kids' logic and reasoning skills. Entire articles have been written about the mathematical theories behind Nim strategy, but you need not delve into that when you just want a no-prep and fun distraction.

Nim is a good early math game that supports addition and subtraction skills. I played a few rounds with my soon-to-be 5th grader and he enjoyed beating me (ahem). But then, my knowledge of mathematical theory is not what it used to be, ha ha ha.

How to play Nim

Nim can be played in various ways and with different quantities. I've chosen a simple version to share with you. We also like to call this game, "counting down."

Materials

• 11 stackable counters. 10 in one color and 1 in a different color. We used black and white poker chips, (affiliate link) which are extremely handy if you play a lot of DIY games at home. You can also use checkers, coins, or even flat blocks.
• 2 enthusiastic players

Objective

Force your opponent to pick up the black (the last) chip.

Rules:

• Stack the white chips on top of the black chip.
• Determine who will go first.
• Taking turns, players picks up 1, 2 or 3 chips from the top of the stack.
• Whoever is left with the last chip loses.

Watch the video to see the game in action:

It's that simple!

Tips and Tricks

TIP: You don't need different color chips for Nim. You can play with 11 chips and whoever is stuck with the last one, loses.

TIP: After 1 or 2 rounds, kids will learn that in order to win they need to leave 4 white counters on top of the black one. If they are able to do that, it becomes impossible for their opponent to win. This will lead to some strategizing and you can start to vary the game rules to tickle their little brains even more (see below for some variation suggestions).

A few questions to ask your kids while they play "counting down":

Is it better to go first or second?

What quantity of white chips do you ultimately want to leave on top of the black one so your opponent can't force you to pick up the black chip?

What happens if you play with 11 white chips and 1 black chip instead? (Try it!)

What happens if you can only remove 1 or 2 chips instead of up to 3? (Try it!)

Benefits of Playing Nim

What are kids learning?

• Counting backwards practices the skills needed for subtraction.
• They are learning to think strategically.
• They are using their reasoning skills.
• They are learning to plan ahead (games like this build executive function).

This post is part of our Camp Mathematics series, an easy, free summer camp curriculum based on having fun while boosting math skills.

More math games to play:

• Tens Go Fish
• Cooperative math dice games
• Magic math triangle
• Array game