Perimeter of Compound Shapes

PROCEDURAL

Mathematics›Measurement|Ages 9—10|ID: mt_n0AlyLQwC9

Measure and calculate the perimeter of composite rectilinear shapes in centimetres and metres

Mastery Evidence

Find the perimeter of an L-shaped figure by identifying all side lengths
Calculate the perimeter of a composite shape where some sides must be deduced
Draw a composite rectilinear shape with a perimeter of 40 cm

Assessment Prompt

“If [child] is given an L-shaped garden plan with all the side measurements labelled, can they add all the sides together to find the total perimeter?”

Prerequisites2

Area of compound shapes
softAges 8—9
Perimeters of polygons
hardAges 8—9

Show full prerequisite tree

Area of compound shapes soft
Decomposing rectilinear figures supports finding missing sides for perimeter
- Understanding angles (age 8+) hard
  Must find rectangle areas before decomposing rectilinear figures into rectangles
  - Area by Tiling hard
    Must see tiling→multiplication connection before computing area via side lengths
    - Area (age 8+) hard
      Counting unit squares is prerequisite to connecting tiling to multiplication
      - Understanding Area hard
        Must understand unit squares and area concept before measuring by counting
        
        Measuring length (age 7+) soft
        Length measurement experience supports understanding area as a 2D measurement
        
        Measuring length (age 6+) hard
        Using standard measurement tools extends measuring with non-standard units
        
        Measuring length and height (age 5+) hard
        Measuring with iterated units extends Y1 beginning to measure length
        
        Comparing Lengths & Heights hard
        Measuring length with units requires first being able to compare lengths directly
        
        Measurable Attributes of Objects hard
        Comparing lengths/heights requires first identifying length as a measurable attribute
        
        Measuring length soft
        Measuring with units benefits from ability to order and compare lengths
        
        Comparing Lengths & Heights hard
        Ordering 3 objects by length and indirect comparison extends direct length comparison
        
        Measurable Attributes of Objects hard
        Comparing lengths/heights requires first identifying length as a measurable attribute
        
        Choosing measurement units soft
        Choosing appropriate tools builds on choosing appropriate units
        
        Capacity and volume hard
        Using standard units for capacity extends from beginning to measure capacity
        
        Comparing Capacity hard
        Measuring capacity with units requires first being able to compare capacities
        
        Measurable Attributes of Objects hard
        Comparing capacity requires understanding capacity as a measurable attribute
        
        Measuring length and height (age 5+) hard
        Using standard units for length extends from beginning to measure length
        
        Comparing Lengths & Heights hard
        Measuring length with units requires first being able to compare lengths directly
        
        Measurable Attributes of Objects hard
        Comparing lengths/heights requires first identifying length as a measurable attribute
        
        Measuring mass and weight hard
        Using standard units for mass extends from beginning to measure mass
        
        Measuring mass and weight (age 4+) hard
        Measuring mass with units requires first being able to compare masses directly
        
        Measurable Attributes of Objects hard
        Comparing mass/weight requires first identifying mass as a measurable attribute
Perimeters of polygons hard
Y4 perimeter of polygons is prerequisite to composite rectilinear perimeter
- Understanding angles (age 8+) soft
  Area of rectangles supports exploring same-perimeter-different-area relationships
  - Area by Tiling hard
    Must see tiling→multiplication connection before computing area via side lengths
    - Area (age 8+) hard
      Counting unit squares is prerequisite to connecting tiling to multiplication
      - Understanding Area hard
        Must understand unit squares and area concept before measuring by counting
        
        Measuring length (age 7+) soft
        Length measurement experience supports understanding area as a 2D measurement
        
        Measuring length (age 6+) hard
        Using standard measurement tools extends measuring with non-standard units
        
        Measuring length and height (age 5+) hard
        Measuring with iterated units extends Y1 beginning to measure length
        
        Comparing Lengths & Heights hard
        Measuring length with units requires first being able to compare lengths directly
        
        Measurable Attributes of Objects hard
        Comparing lengths/heights requires first identifying length as a measurable attribute
        
        Measuring length soft
        Measuring with units benefits from ability to order and compare lengths
        
        Comparing Lengths & Heights hard
        Ordering 3 objects by length and indirect comparison extends direct length comparison
        
        Measurable Attributes of Objects hard
        Comparing lengths/heights requires first identifying length as a measurable attribute
        
        Choosing measurement units soft
        Choosing appropriate tools builds on choosing appropriate units
        
        Capacity and volume hard
        Using standard units for capacity extends from beginning to measure capacity
        
        Comparing Capacity hard
        Measuring capacity with units requires first being able to compare capacities
        
        Measurable Attributes of Objects hard
        Comparing capacity requires understanding capacity as a measurable attribute
        
        Measuring length and height (age 5+) hard
        Using standard units for length extends from beginning to measure length
        
        Comparing Lengths & Heights hard
        Measuring length with units requires first being able to compare lengths directly
        
        Measurable Attributes of Objects hard
        Comparing lengths/heights requires first identifying length as a measurable attribute
        
        Measuring mass and weight hard
        Using standard units for mass extends from beginning to measure mass
        
        Measuring mass and weight (age 4+) hard
        Measuring mass with units requires first being able to compare masses directly
        
        Measurable Attributes of Objects hard
        Comparing mass/weight requires first identifying mass as a measurable attribute
- Measuring Perimeters hard
  Measuring perimeter of simple shapes is prerequisite to perimeter problem solving
  - Calculating with measurements hard
    Measuring perimeter requires measuring lengths and adding them
    - Comparing and ordering measurements hard
      Extends comparing/ordering measures to adding/subtracting them
      - Choosing measurement units hard
        Comparing and ordering measurements with symbols requires being able to measure in standard units
        
        Capacity and volume hard
        Using standard units for capacity extends from beginning to measure capacity
        
        Comparing Capacity hard
        Measuring capacity with units requires first being able to compare capacities
        
        Measurable Attributes of Objects hard
        Comparing capacity requires understanding capacity as a measurable attribute
        
        Measuring length and height (age 5+) hard
        Using standard units for length extends from beginning to measure length
        
        Comparing Lengths & Heights hard
        Measuring length with units requires first being able to compare lengths directly
        
        Measurable Attributes of Objects hard
        Comparing lengths/heights requires first identifying length as a measurable attribute
        
        Measuring mass and weight hard
        Using standard units for mass extends from beginning to measure mass
        
        Measuring mass and weight (age 4+) hard
        Measuring mass with units requires first being able to compare masses directly
        
        Measurable Attributes of Objects hard
        Comparing mass/weight requires first identifying mass as a measurable attribute
      - Comparing and ordering numbers soft
        Using >, <, = for measurements parallels using them for numbers
        
        The two digits of a two-digit number hard
        Comparing two-digit numbers using PV requires understanding tens and ones
        
        A Ten Is Ten Ones hard
        Understanding tens and ones place value requires the concept of 10 as a bundle
        
        The teen numbers hard
        Understanding 10 as a bundle builds on understanding teen numbers as 'a ten and some ones'
        
        How Many in Total? hard
        Understanding tens-and-ones composition requires cardinality — knowing numbers represent quantities
        
        One-to-one counting hard
        Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'
        
        Reading and writing numbers to 20 hard
        Composing/decomposing teen numbers requires reading and writing those numerals
        
        How Many in Total? hard
        Reading/writing numerals 0–20 requires understanding that numerals represent quantities (cardinality)
        
        One-to-one counting hard
        Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'
        
        Writing digits 0-9 hard
        Writing numerals requires the motor skill of forming digits 0-9 (taught in English handwriting)
        
        Sitting and holding a pencil soft
        Same motor skills for digit formation
        
        The teen numbers hard
        General two-digit place value extends from understanding teen number composition
        
        How Many in Total? hard
        Understanding tens-and-ones composition requires cardinality — knowing numbers represent quantities
        
        One-to-one counting hard
        Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'
        
        Reading and writing numbers to 20 hard
        Composing/decomposing teen numbers requires reading and writing those numerals
        
        How Many in Total? hard
        Reading/writing numerals 0–20 requires understanding that numerals represent quantities (cardinality)
        
        One-to-one counting hard
        Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'
        
        Writing digits 0-9 hard
        Writing numerals requires the motor skill of forming digits 0-9 (taught in English handwriting)
        
        Sitting and holding a pencil soft
        Same motor skills for digit formation
        
        Two written numerals between 1 and 10 soft
        Comparing two-digit numbers extends from comparing single-digit written numerals
        
        Comparing groups: more or fewer soft
        Comparing written numerals is the symbolic form of comparing quantities — conceptual comparison helps but isn't strictly required
        
        Counting objects to 20 soft
        Counting a set helps when comparing groups, but younger children (GB age 4) can compare using matching without formal counting to 20
        
        How Many in Total? hard
        Answering 'how many?' requires the cardinality principle
        
        One-to-one counting hard
        Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'
        
        One-to-one counting hard
        Counting objects to answer 'how many?' requires one-to-one correspondence
    - Choosing measurement units hard
      Extends Y2 standard unit measurement to include mm and to add/subtract measures
      - Capacity and volume hard
        Using standard units for capacity extends from beginning to measure capacity
        
        Comparing Capacity hard
        Measuring capacity with units requires first being able to compare capacities
        
        Measurable Attributes of Objects hard
        Comparing capacity requires understanding capacity as a measurable attribute
      - Measuring length and height (age 5+) hard
        Using standard units for length extends from beginning to measure length
        
        Comparing Lengths & Heights hard
        Measuring length with units requires first being able to compare lengths directly
        
        Measurable Attributes of Objects hard
        Comparing lengths/heights requires first identifying length as a measurable attribute
      - Measuring mass and weight hard
        Using standard units for mass extends from beginning to measure mass
        
        Measuring mass and weight (age 4+) hard
        Measuring mass with units requires first being able to compare masses directly
        
        Measurable Attributes of Objects hard
        Comparing mass/weight requires first identifying mass as a measurable attribute
  - 2-D shapes (age 6+) soft
    Perimeter of 2-D shapes requires knowing shape properties (number of sides)
    - Angles in triangles (age 6+) soft
      Understanding defining attributes supports describing shape properties formally
      - 2-D shapes hard
        Distinguishing defining vs non-defining attributes requires knowing common 2-D shape names first
      - 3-D shapes (age 5+) hard
        Identifying defining attributes builds on informal analysis and comparison of shapes
        
        2-D shapes hard
        Analysing and comparing shapes requires being able to name them first
        
        3-D shapes hard
        Analysing 3-D shapes requires recognising and naming them
    - 2-D shapes hard
      Describing properties of 2-D shapes (sides, symmetry) requires knowing the shapes first
    - 3-D shapes (age 5+) hard
      Formal property description extends informal analysis of sides and vertices
      - 2-D shapes hard
        Analysing and comparing shapes requires being able to name them first
      - 3-D shapes hard
        Analysing 3-D shapes requires recognising and naming them

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