I used to provide active maths workshops for primary school teachers. The workshops were really a series of games with a clear mathematical element.  Everyone’s favourite was a game I invented called Number Police. It is easy to differentiate and extend, full of lively discussion and teamwork and most importantly – full of drama.

You can play this with a large group or as a family of four.

How it works:

Split the group into two halves.  Half the group are policemen, half are police informants. The police are looking for a number who is suspected of committing a crime. Quietly, informants decide what number is guilty (1-100).  Good ones to start with are numbers with lots of factors (e.g. 48). Police have all the numbers from 0 to 100 lined up on a ‘suspect board’ (or on the floor). Print out a 100 square or with a big group, the game works particularly well with a set of 100 numbered carpet tiles.

One at a time, informants call up the police station on a telephone (two telephones and a telephone sound effect are perfect here, but not necessary).  Each informant must provide a clue to help the police to eliminate some of the numbers from their suspect lists. E.g. ‘The number you are looking for is even’ or ‘The number you are looking for is a multiple of 4’ or ‘The number you are looking for has a 2 in it” or “The number you are looking for is three more than a prime number” or “When you add this numbers digits together, you get 10”.  The police then have a meeting to discuss what they have learnt from the informant and which numbers they can now eliminate from their enquiries.  As the police eliminate suspect numbers they turn them over. They are left with the number that caused the crime.


  • Use more complicated clues – encourage participants to use more complex mathematical language.
  • You can limit the number of clues the informants are allowed to give and specify the language they must use in clues e.g. factor, greater than, divisible by….
  • Have a tick list of language that they must use, and cross it off when an informant has used a particular keyword – limiting the selection for the remaining informants.
  • Try switching it around so that the police are interviewing the informants and asking specific questions – but are only allowed to ask a certain number of questions to reach the answer.


Make sure that the police hold their meeting after each clue has happened.  There are always some super keen policeman that will dive right in without discussion and this can cause problems.  For example if the clue is “The number you are looking for is divisible by three”, then the policemen must discuss which numbers are therefore turned over (or crossed out – if using a paper 100 square).  They must turn over/eliminate all the numbers that are NOT divisible by 3.  Those that dive in may not have thought this through properly and will busily be going through the 3x table in their head and happily getting rid of all the suspects.

More than maths

This activity requires discussion, co-operation and teamwork.  There is a great deal of speaking and listening integrated within the maths.  This activity can also be very dramatic – picture the informants trying to get to the telephone without being spotted, glancing around them to see if they are being watched… picture the stereotypical policeman answering the phone with an “‘ello, ‘ello, ‘ello”.  Maths – disguised in a drama game.