Percentages

INTRODUCE

PRESENTATION: If the world were a village…

The word “percentage” comes from the latin “per centum” which means ‘for every hundred’. The above presentation gets students to really think about that phrase: ‘for every hundred’. They are asked to imagine the world was represented by a village of only 100 people and determine how many people in the village exhibit particular characteristics.

The students are required to think about percentages, perhaps without realising that they are doing so. Percentages are included on the pie chart, which should give you the opportunity to introduce percentages in a natural way, linking them to the world village.

Another good way to use this presentation is to get the students to think about some other ways of representing the data by converting the percentages to decimals or fractions.

This video is a very good visual aid to explain a lot of the information found in the presentation. Note, some of the figures are slightly different as they have been obtained from different sources.


APPLY & AMAZE

PRESENTATION: Being Number One

Bendford’s Law states that the frequency of each possible leading digit of naturally occurring sets of numbers is not equal. In fact, 1 is far more common as a leading digit and 9 is far less common. Initially, this is a somewhat counterintuitive idea; many of us presume that each leading digit has an equal probability of occurring.

Bedford’s Law has some extremely useful applications, especially when investigating fraud. Accountants will use Benford’s Law to determine if data they are given seems naturally occurring or seems as though it may have been made up. The above presentation gives your students the opportunity to test this theory by getting them to make up some figures of their own and then test if they follow Benford’s Law.

Numberphile do a great job of explaining Benford’s Law in a bit more detail, which you could use if you wanted to give your students more information about why it works.

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