# 3. Solving measurement problems

Much of the practical work that goes on in schools and universities involves students following detailed instructions. In some contexts, this is very important but it can lead to students losing sight of why they are being asked to do a particular thing. It is good for students to have the opportunity to design their own experiments. In Activity 3 they have to design an experiment to solve a particular problem. There will be more than one solution. This would be an opportunity to divide your students into mixed ability groups. The students who find the work quite easy will be able to help those who find it more difficult and in doing so will consolidate their own understanding. In Case study 3 the teacher uses some amazing facts to motivate her students and gets them to do some estimating so they can get a ‘feel’ for different masses and lengths.

## Case study 3: Estimating size

Mrs Nakintu went to an internet café and looked up some interesting facts about the Earth – she found the mass of the Earth and its circumference, the length and breadth of their country, the distance to the moon, the distance to the sun (see Resource 5). She started the lesson by putting her students in groups and asking them to guess the answers to the questions. To make it a bit easier she wrote three possible answers on the board for each question and they had to select the correct one. The idea was to help her students understand the range of measurements that can be made and to get them interested

She then gave them some everyday objects and asked them to guess the mass or the length. She also asked them to estimate the size of the room. Each group wrote their answers on a piece of paper and handed it in.

She gave the pieces of paper out (so each group had answers by a different group) and asked different students to make the measurements. She wrote the answers on the board and the groups marked each other’s work – 3 marks if they were within 10%, 2 marks if they were within 50% and 1 mark if they got the right order of magnitude. It did not take very long and the class enjoyed themselves.

## Activity 3: Solving problems

This is a problem-solving exercise. Divide the class into eight groups. Choose four problems, so that pairs of groups are given the same problem. The problems involve using a combination of instruments or creative thinking to make a measurement that cannot be made directly.

Suggested problems could be finding the height of a tree, finding the volume of a stone, finding the mass of one sheet of paper, finding the area of the palm of your hand, finding the thickness of one piece of paper, finding the mass of a grain of rice, finding the pressure exerted by a student on the ground.

Students compare what they did and the answer they got with the other group and evaluate their own work. Groups who solve their problem easily can be given another one to do.

2. Organising a ‘circus’ of experiments

Resource 1: Differentiating Work