Money thinking

Maria, a journalist with school-aged children, is able to deal with decimals in many situations by relating them to money. Maria does not realise that she has a problem. Her interpretation of money in terms of numbers of dollars and numbers of cents means that she does not appreciate the underlying structure of decimals. She disregards digits which lie outside her narrow field of vision; any digits past two decimal places. Money thinking appears to be the same as expert behaviour until long decimals are required.


Look at Maria's answers to the Decimal Comparison Test. (You can double-click on the yellow notes for her reasons).

Interviews with Maria
Talking About Place Value Video Images with text
Making the Biggest and Smallest Numbers Video Images with text
Number Between Video Images with text
Hidden Numbers Video Images with text

Attempt a short decimal comparison test to check your understanding of Maria's thinking. This will help you learn to diagnose this error.

Lesson ideas appropriate for students like Maria.

Research on our Australian sample shows that the percentage of students using money thinking increases with age (about 6% of Year 10 students and some tertiary students). A full description of money thinking.