List

Hidden Treasures

To celebrate NRICH's 20th birthday, we've taken a look back in the archives and dusted off some problems from the early days, freshened them up, and added some new ideas. We hope you enjoy working on these hidden treasures!
Calendar Capers
problem

Calendar Capers

Age
11 to 14
Challenge level
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Choose any three by three square of dates on a calendar page...
Counting Factors
problem
Favourite

Counting Factors

Age
11 to 14
Challenge level
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Is there an efficient way to work out how many factors a large number has?
Latin Numbers
problem
Favourite

Latin Numbers

Age
14 to 16
Challenge level
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Can you create a Latin Square from multiples of a six digit number?
Building Tetrahedra
problem

Building Tetrahedra

Age
14 to 16
Challenge level
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Can you make a tetrahedron whose faces all have the same perimeter?
Gift of Gems
problem

Gift of Gems

Age
14 to 16
Challenge level
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Four jewellers share their stock. Can you work out the relative values of their gems?
Rationals Between...
problem

Rationals Between...

Age
14 to 16
Challenge level
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What fractions can you find between the square roots of 65 and 67?