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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?

Missing Multipliers

Stage: 3 Challenge Level: Challenge Level:1
Below is a screenshot of a Missing Multiplier challenge with some of the cells revealed.
Missing multiplier grid
What must be the value of A?
How does that help you to work out B, C and D?
Can you use a similar strategy to work out E, F, G and H?