Crossing the Bridge
Age 11 to 18
Challenge Level
Four friends must cross a bridge. How can they all cross it in just 17 minutes?
Last Biscuit
Age 11 to 18
Challenge Level
Can you find a strategy that ensures you get to take the last biscuit in this game?
Clock Arithmetic
Age 11 to 18
Challenge Level
What happens if we change the rules and make the usual straight number line into a circle?
Clock Squares
Age 14 to 18
Challenge Level
Can you find a way of predicting the value of large square numbers with the help of our power modulo calculator?
More Adventures with Modular Arithmetic
Age 14 to 18
Challenge Level
Investigate what happens when we add or multiply numbers using modular arithmetic.
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NRICH is part of the family of activities in the Millennium Mathematics Project.
NRICH is part of the family of activities in the Millennium Mathematics Project.