Broken Calculator

broken calculator activity
Broken Calculator by Transum.org

A fun activity with some thinking necessary…

Children are asked to click the available keys on the ‘broken’ calculator above to make the numbers 1 – 20. As  each total is achieved the calculation used to achieve a given number will appear in the table on the right.Those who manage to make all twenty totals earn a ‘Transum Trophy’ – a certificate sent to their email (or their teacher’s email if they wish!).


Unlike a normal calculator, for this activity, you cannot use one total you have found to help make another. Each calculation starts from scratch (zero). I also noted that any multiplications are treated as though they are in brackets… they’ll figure it out! Try to make each total using the fewest number of calculator key presses.

Other broken calculators are available from the links within the activity: 1 & 5,  2 & 3,  3 & 4,  4 & 5, 5 $ 2

The activity is tablet friendly and plays well on my elderly iPad mini.


Broken Calculator by Transum.org