Why play this game?
Countdown offers a motivating context in which to practise calculation strategies. It encourages learners to estimate and to 'tinker' with solutions so as to get closer to the target number. ('Tinkering' is one of the mathematical habits of mind
referred to by Al Cuoco et al.)
Introduce the game to the group, asking them to choose any six cards. (The top row contains the numbers 25, 50, 75, 100 and the bottom row contains numbers from 1 to 10.) Explain that the computer will give a target number and then the aim of the game is to use the chosen numbers and the four standard operations (addition, subtraction, multiplication and division) to hit the target.
Emphasise that each card can only be used once and that it may not be necessary to use all the cards.
The first time you play, you could give a time limit (for example three minutes). Encourage learners to get as close to the target as they can. If they manage to hit the target within the time limit, they could try to find an alternative way of doing it.
Once the time is up, invite students to share strategies, perhaps in pairs or small groups. You could select a couple of learners to share their method with the whole class. You may wish to instigate a discussion on the advantages of each method and therefore which might be more efficient. It would be worthwhile to collect strategies on a 'working wall' so the whole group can
look back and see which prove useful time and time again.
If no-one has found a solution, you could leave the challenge on the wall as a 'simmering' activity for a few days so that members of the group can come back to it in their own time.
A cooperative version of this game could involve working with a partner to find a solution and then looking back over several 'goes' to begin to develop a bank of useful strategies.
(It is always possible to hit the target. Clicking on "Show a solution" will offer one possible way in which the target can be reached, but it will not necessarily be the most efficient solution.)
How could you use rounding and estimation to help?
How could you get close
to the target?
offers a much more challenging version of the game.
Students could work in pairs rather than isolation. You could, for example, always allow use of the number 10 and/or 100, whether they are selected or not.