The Countdown Numbers Game  

Samir Khan 

Adept Scientific plc, 

samir.khan@adeptscience.co.uk 

Countdown is a popular numbers and letters quiz program on UK television.  In one of the rounds, the contestants must use a range of basic arithmetic operations (addition, subtraction, multiplication and division) to make six seed numbers equal a target.   

The seed numbers are randomly selected from a restsricted set of large numbers (25, 50, 75 and 100) and small numbers (1 to 9), and the target is a random integer between 101 and 999.  Not all the seeds have to be used, but each can only be used as many times as it appears. 

• Seed and target numbers can be randomly generated or manually specified.  If randomly generated, two seeds will be large numbers, with the remaining seeds small numbers.

• The worksheet halts execution as soon as the first solution is found (although there may be many other, possibly simpler, solutions).

• If the target cannot be found after searching the solution space, then the closest solution will be returned.  This can take several minutes.