Year 4 · Measures, time and graphs
Perimeter of rectilinear shapes
Measure and calculate the perimeter of a rectilinear figure, including squares, in centimetres and metres
Lesson overview
What you'll learn in this lesson
Measure and calculate the perimeter of a rectilinear figure, including squares, in centimetres and metres
Key learning points
- • Walk round the shape
- • Perimeter is not area
- • L-shapes and missing sides
- • Working backwards
This lesson at a glance
- 20 minutes
- 19 parts to scroll through
- 4 quick checks
- No marked quiz yet
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 19
Watch first
Perimeter of rectilinear shapes
Measuring round the edge, covering the inside, then reading the clock.
Read the film in words (English) ↓
What the film shows
- A finger traces the edge of a rectangle while the perimeter total counts up.
- The same rectangle fills with unit squares to show its area.
- Units convert on screen: centimetres to metres, grams to kilograms, millilitres to litres.
- A 12-hour clock and a 24-hour clock show the same moment side by side, then a bar chart is read off.
- The perimeter and unit-swap practicals for this unit repeat all of this with a tape measure.
Do it for real
The practicals below use what the film shows, with a full method you can follow at home.
In a nutshell
Measure and calculate the perimeter of a rectilinear figure, including squares, in centimetres and metres
What you already know
Part 2 of 19
Before we start
What you already know
You can find area by counting squares and add several numbers together.
Key words
Part 3 of 19
Key words
Words you'll need today
- perimeter
- The total distance around the outside of a shape.
- rectilinear
- A shape made only of straight sides and right angles.
- opposite sides
- The sides facing each other, equal in a rectangle.
Learning cycle
Part 4 of 19
Learning cycle 1 of 2
Part 1 — Adding the edges
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 5 of 19
Learn
Walk round the shape
A rectangle 8 cm by 3 cm has perimeter 8 + 3 + 8 + 3 = 22 cm. Because opposite sides are equal, you can also add one long and one short side and double it: (8 + 3) × 2 = 22 cm.
Explore the idea
Part 6 of 19
Learn
Perimeter is not area
Perimeter is measured in cm or m; area is measured in cm² or m². Two shapes can have the same area but different perimeters — a long thin rectangle has far more edge than a square with the same area.
Quick check
Part 7 of 19
Quick check
Perimeter of a 6 cm by 4 cm rectangle:
Quick check
Part 8 of 19
Quick check
A square has sides of 7 m. Its perimeter is
Reset break
Part 9 of 19
Pause
That's sitting 1 of 2 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 10 of 19
Learning cycle 2 of 2
Part 2 — Missing sides
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 11 of 19
Learn
L-shapes and missing sides
In an L-shape, the two short horizontal sides always add up to the long one, and the same is true vertically. Use that to work out any length that has not been printed, then add all the sides as usual.
Explore the idea
Part 12 of 19
Learn
Working backwards
A square has perimeter 20 cm, so each side is 20 ÷ 4 = 5 cm. A rectangle with perimeter 30 cm and one side 10 cm: half the perimeter is 15 cm, so the other side is 5 cm. Halving first saves a lot of trial and error.
Quick check
Part 13 of 19
Quick check
A square has perimeter 36 cm. Each side is
Quick check
Part 14 of 19
Quick check
Perimeter is measured in
Common mix-ups
Part 15 of 19
Common mix-ups
Things people often get wrong
- Multiplying the two sides, which gives area instead of perimeter.
- Adding only two sides of a rectangle.
- Leaving a missing side out of an L-shape total.
Challenge round
Part 16 of 19
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Challenge round
Part 17 of 19
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
A rectangle 8 cm by 3 cm has ____ 8 + 3 + 8 + 3 = 22 cm.
Mastery quiz
Part 18 of 19
No quiz for this one
This lesson has no marked quiz attached yet.
Lesson round-up
Part 19 of 19
Lesson round-up
Ready when you are
Quiz score
Not sat
Games
Not played
Points this lesson
0
Best run
0 in a row
Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?
Ask LunaDo the work
Your written work for this lesson
This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.
The cost of a school trip
A school is planning a trip to a wildlife park. The coach costs £480 however many people go. Entry costs £9.50 for each pupil and each adult goes free. The school says every pupil must pay the same amount, and the trip must not lose money.
If 60 pupils go, the coach works out at £8 each, so the total for each pupil is £17.50. If only 40 pupils go, the coach works out at £12 each, so the price rises to £21.50. The teacher explains that the coach is a fixed cost and the entry is a cost per person — which is why the price per pupil changes when the number changes.
The school decides to charge £20 and to use anything left over for a second trip later in the year.
Written for Good Learning Co.
Reading questions
- Work out the total cost of the trip if 50 pupils go.
- Show why the price per pupil falls when more pupils go, using numbers.
- At £20 each, how many pupils must go before the trip makes money? Show your working.
Working out
Working outDo the practice questions on paper, showing every step — not just the answer. Mark them yourself and circle anything you got wrong.
10–15 questions
Worked example, explained
WritingCopy one question out and write underneath, in words, why each step works.
1 question, 4–5 sentences
Problem in words
Working outWrite your own real-life problem that uses today's method, then solve it.
1 problem + solution
Saved as you type.
Part 1 of 19 · Watch & discover