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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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Adding All Nine

Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!

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Have You Got It?

Can you explain the strategy for winning this game with any target?

Product Sudoku

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Alison and Charlie kept a record of the order in which they filled the Sudoku.
They filled the cell marked 1 first, then the cell marked 2, then the cell marked 3...
 
You might like to retrace their route to fill in the cells in the same order, though this is just one possible route through the problem.

You can print their journey here