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Counting Counters

Take a counter and surround it by a ring of other counters that MUST touch two others. How many are needed?

Cuisenaire Squares

These squares have been made from Cuisenaire rods. Can you describe the pattern? What would the next square look like?


We can arrange dots in a similar way to the 5 on a dice and they usually sit quite well into a rectangular shape. How many altogether in this 3 by 5? What happens for other sizes?

Celebrate 25 Years of NRICH

Age 5 to 14

To celebrate NRICH's 25th birthday, we have created a special version of one of our favourite games, Got It.

Got It is a game for two players.

The challenge is to be the first player to hit the target of 25 (as a celebration of NRICH's birthday!).

  • You can play against the computer or with a friend. 
  • The first player chooses a whole number from 1 to 5.
  • The second player chooses a whole number from 1 to 5, which is added onto the first player's number to make a new total.
  • Play continues in this way, with players taking turns to add a whole number from 1 to 5 to the running total.
  • The winner is the player who reaches the target of 25.

Play the game several times.

  • Can you find a winning strategy?
  • Can you always win?

Does your strategy depend on whether or not you go first?

To change the game, choose a new Got It target or a new range of numbers to add on.

Test out the strategy you found earlier. Does it need adapting?

  • Can you work out a winning strategy for any target?
  • Can you work out a winning strategy for any range of numbers?
  • Is it best to start the game? Always?

Away from the computer, challenge your friends:
One of you names the target and range and lets the other player start.


  • Can you play without writing anything down?
  • Consider playing the game where a player CANNOT add the same number as that used previously by the opponent.