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# How long is a piece of string?

Present students with a piece of string (4–5 metres) and discuss how to estimate its length. Show students how a standard informal measure can be used as a benchmark to estimate the length of the string.

Watch the *Armspan *video which explains the process.

You can download the *Armspan* video transcript.

The body proportions of children and teenagers differ from those of adults. To compare, measure the arm span for each student in the class using the 1 metre benchmark method.

Use the data to draw a histogram to demonstrate the variation in the arm span measurement amongst the students.

Calculate the mean of the class data and compare it with the benchmark measurement for adults of 1 metre.

Use the average arm span length calculated from the class data to gain an estimate of the length of the string.

Measure the string using a tape measure and compare the estimate to the exact length of the string.