### Pebbles

Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?

### It Figures

Suppose we allow ourselves to use three numbers less than 10 and multiply them together. How many different products can you find? How do you know you've got them all?

### Bracelets

Investigate the different shaped bracelets you could make from 18 different spherical beads. How do they compare if you use 24 beads?

# What Do You Need?

##### Stage: 2 Challenge Level:

What do you need to find a chosen number from this hundred square?

Four of the clues below are true but do nothing to help in finding the number.
Four of the clues are necessary for finding it.

Here are eight clues to use:
1. The number is greater than $9$.
2. The number is not a multiple of $10$.
3. The number is a multiple of $7$.
4. The number is odd.
5. The number is not a multiple of $11$.
6. The number is less than $200$.
7. Its ones digit is larger than its tens digit.
8. Its tens digit is odd.
What is the number?

Can you sort out the four clues that help and the four clues that do not help in finding it?