Estimate the lengths of these lines in centimetres.
Add your estimates together.
Hint: Your classroom door is probably two metres tall. How do the lines compare to that length?
Topics: Starter  Estimating
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Previous Day  This starter is for 2 September  Next Day
The answer will vary depending on how large your projector image is. Use a tape measure or ruler to measure the lines then add the results together. Who in the class got closest to the sum of your measurements?
Note to teacher: Doing this activity once with a class helps students develop strategies. It is only when they do this activity a second time that they will have the opportunity to practise those strategies. That is when the learning is consolidated. Click the button above to regenerate another version of this starter from random numbers.
Teaching idea: Allow the pupils to work on this activity without any help. Once they have arrived at an answer, collect ideas from the class about strategies used then give the pupils a chance to reestimate the lengths. As a point of reference, the classroom door is probably around 2m tall. Use a large ruler to find the correct lengths but stress that getting the answer exactly right was not expected.
Presentation Tip: Press the F11 key (except on MS Edge) to hide the tool bars if the lines don't fit on to your screen. You can also use the zoom option in your browser's menu to vary the display size.
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Teacher, do your students have access to computers such as tablets, iPads or Laptops? This page was really designed for projection on a whiteboard but if you really want the students to have access to it here is a concise URL for a version of this page without the comments: Transum.org/go/?Start=September2 However it would be better to assign one of the student interactive activities below. 

Here is the URL which will take them to a related student activity.
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