Look at the following row of numbers:

## $$10\quad 15\quad 21\quad 4\quad 5$$

They are arranged so that each pair of adjacent numbers adds up to a square number: $$10 + 15 = 25$$ $$15 + 21 = 36$$ $$21 + 4 = 25$$ $$4 + 5 = 9$$

**Can you arrange the numbers 1 to 17 in a row in the same way, so that each adjacent pair adds up to a square number?**

This printable set of

cards might help you to test different options.

**Can you arrange them in more than one way? If not, can you justify that your solution is unique?**

Printable NRICH Roadshow resource.