Here are nine triangles. Each one has three numbers on it.
Your challenge is to arrange these triangles to make one big triangle, so the numbers that touch add up to 10.
Once you've finished making the big triangle, think about these questions:
How did you get started?
What did you do next?
You can print out the sheet at the top of this page and cut the triangles out, then try arranging them.
If you prefer, you can also use a printable version of the triangles with numbers represented on tens frames.
Alternatively, you might like to use this interactivity, which allows you to drag each triangle onto the large triangle.