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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?

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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?

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Bracelets

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

Multiples Grid

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

There is a clue in the title of the problem!
You may like to investigate this spreadsheet which shades the numbers on the $100$ square. The pictures have been taken from this spreadsheet. Can you see what is happening?
Are there some answers which you can rule out straight away in each case?
How will you know you have all the solutions for each grid?