Broken Calculators

There are certain Maths activities that seem to engage students without fail. Broken calculator activities is one of these.

The flash interactive at subtangent has six levels and a time limit on each.

Try this broken calculator which allows you to set which keys are broken. also have some good interactives such as this one.

I first encountered a broken calculator question in the 1980’s. At first sight I did not think it possible. My colleague Keith soon set me straight.

Here is the exact question. See how you go!

Keith is very upset. A lot of buttons on his calculator are not working. In fact only the 1, 3 and 5 numerals work. However, the “division”, the “equals” and the “decimal point” buttons also work. The teacher asks Keith’s class to find different ways of getting the answers 1 to 20 on a calculator. Help Keith get all the answers on his broken calculator.



About webmaths

I have been teaching Mathematics in Victorian secondary schools for 30 years. I use the www to make my maths lessons better. I hope this blog will give other teachers some ideas to try in their own classes.
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