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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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For this challenge, you'll need to play Got It! Can you explain the strategy for winning this game with any target?

Product 100

Stage: 3 Short Challenge Level: Challenge Level:1

The product of four different positive integers is 100. What is the sum of these four integers?

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.


This problem is taken from the UKMT Mathematical Challenges.
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