### Why do this
problem?

This problem is a good context in which to discuss different,
and perhaps most efficient, methods of calculation.

### Key questions

Why don't you try adding all the one-digit numbers
first?

Can you describe what you did?

Are there any quicker ways of doing it?

### Possible support

Learners could find the sum of the one-digit whole numbers
first and then the two-digit whole numbers instead.