Number adding triangle

There are a lot of challenges you can set with this simple structure and set of rules.

The basic rules are:

  • Each number must be the sum of the 2 numbers below it
  • You can only use a number once

Here’s an example of one of the basic rules:

Here’s two examples of completed number triangles. But something’s wrong. What are the problems in each?


How many arrangements of odd and even are there? Can you find them all?
  1. What’s the lowest possible number that you can get in the top circle?
  2. Can you fill it with only odd numbers? If so, do it. If not, say why not.
  3. The number in the top is always bigger than the sum of numbers in the bottom row. Why is that?
  4. Can you get the number 10 in the top circle. How many different ways can you do it?
  5. Instead of the numbers, just put in if it’s odd or even and see how many different odd/even patterns you can come up with.

To try these at home or in class, download the activity pack (or just draw your own on paper)

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