# 5 Units of measurement and working with bigger dimensions

In the last section you focused on the measurements used in working out area and perimeter. Students tend to be told to use units of measurements such as metres, centimetres, inches, etc. but without letting them understand from their own experience why it is actually a good idea to do so. A unit of measurement is a measure defined and adopted as a standard by convention or by law, such as a metre, a gram or a litre.

In the next activity you will ask your students to explore in groups any areas and perimeters they can find outside the classroom using their own measures, and then to compare and discuss their findings with other students in the class. Taking the mathematics outside of the classroom in this way also allows the students to become aware that mathematics is all around us. At the same time, it gives them the opportunity to experience working with larger shapes than pencil and paper allow.

## Activity 5: Finding out area and perimeter of large regular shapes using different unit measures

This out-of-the-classroom activity works well when students work in groups of four or five and they have been assigned roles within their groups. For example, two students can be asked to measure, one student to oversee, one or two students to record the observations. If your students have access to digital cameras or mobile phones with an integral camera, these could be used to take photographs of the shapes that the students measure in their groups. Alternatively, a tape recorder could be used to record the measurements instead of writing them down when the students are working out-of-the-classroom.

### Part 1: Working out perimeter and area of large shapes

The task you are asking the students to do is to measure and work out the perimeter of as many large shapes as they can within a certain time period outside of the classroom. For example, they could measure the perimeter and area of the playground, the flower bed, the water pump area. Decide with the students on a list of which shapes to measure so that the measurements can be compared later.

The students are not to use any metric measures like metres, but their own ‘measures’ such as sticks, feet, steps, etc.

### Part 2: Comparing findings

Back in the classroom, ask the students for their findings and write these on the blackboard.

Ask the students whether they came up with the same measurements. What was the same and what was different? Did they encounter any difficulties when measuring? Can they think of more effective and accurate ways to make such measurements?

## Case Study 5 : Mr Mehta reflects on using Activity 5

The class thought it would be very easy to complete this activity but when they actually started they found that there were a lot of challenges. Some used a piece of wood they found, some used their tread length, some used their arm length and so on.

During the discussion we found that the pupils had been wondering what to write for units. This helped them realise that there was an issue about comparisons when each group uses a different ‘unit’ of measurement. They came up with the suggestion themselves that using standard units of measurement might be a good idea!

During the discussion, the students talked about aspects of dimension as well as different dimensional measurements in a playful way, such as describing the area in twig2!

4 Making a distinction between the concepts of area and perimeter