### Counting Counters

Take a counter and surround it by a ring of other counters that MUST touch two others. How many are needed?

### Cuisenaire Rods

These squares have been made from Cuisenaire rods. Can you describe the pattern? What would the next square look like?

### Doplication

We can arrange dots in a similar way to the 5 on a dice and they usually sit quite well into a rectangular shape. How many altogether in this 3 by 5? What happens for other sizes?

# Fault-free Rectangles

##### Age 7 to 11 Challenge Level:

This rectangle is made from six 2 by 1 rectangles:

You can see it has a line going through the middle from the top edge to the bottom edge. This means that the rectangle could be broken into two and so the line is called a fault-line.

Can you make a rectangle without a fault-line (a "fault-free" rectangle) with one white and four red rods?

What do you notice about the way you have made the shape?

Can you use what you have noticed to make a fault-free rectangle with red and light green rods?

Can you make any similar fault-free rectangles with rods of other colours?

Can you find the smallest fault-free rectangle that can be made using 2 by 1 rectangles?

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We would like to thank Geoff Faux for introducing us to the idea of fault free rectangles.