Ask the class to read the second side of the worksheet in silence for two minutes while they think of a plan to work out how many times each gear will turn. Discuss their plans in small groups and then brainstorm ideas on the board. Invite the groups to choose a plan, write it down and start working. Stop the class after ten minutes and ask selected groups to explain any ways in which they can predict the number of turns. Pupils then continue working but may, if they wish, modify their plans.
Lead pupils towards the use of ratio.
In the final reporting back session, the teacher should try to discuss and formalise some of the informal learning about ratio which has taken place. These level indicators should be used in accordance with the assessment guidance given on page 16 . Level four Organises work following own strategy but does not include all possible cases, or does so only under the direction of the teacher or other pupils. Writes results clearly and collects at least three sets of results. Level five Works systematically and checks work to ensure all cases covered.