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Cotmanhay Junior School

Safe, Happy Learning

Week 7 - 9 Length and perimeter

National curriculum content

  • Measure, compare, add and subtract lengths
  • Measure the perimeter of simple 2-D shapes


Lesson objectives

  1. Measure length
  2. Measure length (m)
  3. Equivalent lengths – m & cm
  4. Equivalent lengths – mm & cm
  5. Compare lengths
  6. Compare lengths
  7. Add lengths
  8. Subtract lengths
  9. Measure perimeter
  10. Calculate perimeter


What we want children to know

  • Use different measuring equipment including rulers, tape measures, metre sticks and trundle wheels
  • Measure larger objects using metres
  • Think about whether it is better to measure items in centimetres or metres
  • Recognise that 10 mm is equivalent to 1 cm
  • Compare lengths of objects using comparison language and symbols
  • Use language such as longer than, shorter than, taller than, longest, shortest and tallest
  • Convert measurements to the same unit of length to add
  • Explore the most efficient way to calculate and develop their mental addition strategies
  • Measure the perimeter of simple 2D shapes
  • Explore different methods for calculating the perimeter of a shape


What skills we want children to develop

Use knowledge to solve reasoning and problem solving questions such as:


Position the symbol:

Place the correct symbol between the measurements > or <

e.g. 306cm __ half a metre


Testing conditions:

A square has sides of a whole number of centimetres. Which of the following measurements could represent its perimeter?

8cm                18cm              24cm              25cm


Top tips:

Ahmed’s ruler is broken. Explain how he can still use it to measure things in the classroom.


Mathematical talk

  • What unit of measure would be best to measure ____?
  • How many millimetres are in ½ cm?
  • Which symbols can we use to compare lengths?
  • Why does converting the measurements to the same unit of length make it easier to add them?
  • What is the most efficient way to subtract mixed units?
  • What is perimeter? How can we calculate the perimeter of each shape?