Mathematics

Intermediate

50 mins

Teacher/Student led

Learning Goals

Learning Outcomes

Lesson Files

+65 XP

What you need:
IWB/Projector/Large Screen
squared paper
Traced shape templates

Estimating and Measuring the Area of Irregular Shapes

Estimate the area of irregular shapes by counting whole squares and pairing part-squares on a grid. Understand why this method gives an estimate rather than an exact measurement.

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1 Getting Started
2 Watch and Notice
3 Try It Together
4 Trace and Tally in Your Copy
5 Class Challenge
Pupil practice

1 - Getting Started ~4 mins

Illustration for Getting Started Look at the leaf on the grid of centimetre squares. Its edges curve in and out, with no straight sides at all.

How could we work out the area of something with no straight edges? Length times breadth won't help us here.

👇 Mark your steps as done as you complete them.

+5 XP

2 - Watch and Notice ~9 mins

Illustration for Watch and Notice We have a leaf drawn on a grid of squares. First we will count the squares the leaf covers completely — the certain ones. Then we will look at the squares along the curved edge and work out which of those to count. Watch how we decide what to do with a part-covered square.

👇 Mark your steps as done as you complete them.

+10 XP

3 - Try It Together ~10 mins

Key point

Today we estimate the area of one leaf together. First we count every whole square inside the outline. Then we go round the curved edge and decide each part-square with the more-than-half rule. Last we pair up any leftover half-squares to make wholes.

Hands-on Task

+15 XP

4 - Trace and Tally in Your Copy ~3 mins

COPYBOOK MOMENT

In your maths copy, trace an irregular shape onto squared paper. Then make two columns and tally them:

Whole squares
Part-squares (counted using the more-than-half rule)

Add them together and write your area estimate in cm².

+10 XP

5 - Class Challenge ~11 mins

Key point

Work on your own squared paper at your desk. Estimate the area of three irregular shapes, each one wigglier than the last. For every shape: count the whole squares, pair up the part-squares to make whole squares, and record your total estimate in cm².

Shape 1: a rounded stone outline (gentle curves).
Shape 2: a leaf with a pointed tip and a wavy edge.
Shape 3: your own hand, fingers spread, traced round.

Hands-on Task

+15 XP

Pupil practice

Module 5 · Measures: Length, Area, Volume, Mass and Capacity Measures

Lesson 55 · Estimating and Measuring the Area of Irregular Shapes

Download Activity Book page (PDF)

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Estimating and Measuring the Area of Irregular Shapes

Teacher Class Feed

1 - Getting Started ~4 mins

2 - Watch and Notice ~9 mins

3 - Try It Together ~10 mins

Hands-on Task

4 - Trace and Tally in Your Copy ~3 mins

5 - Class Challenge ~11 mins

Hands-on Task

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