Year 4 · Perimeter, Area and Measures · Summary

Year 4 Perimeter, Area and Measures: summary and key words

Part of the Year 4 perimeter, area and measures chapter. Chapter overview · whole chapter on one page

Chapter summary

Skill	Method
Reading a ruler	10 mm = 1 cm. Start at 0. Read the whole cm, then count the mm. 7 cm 4 mm = 74 mm = 7.4 cm. If it does not start at 0, subtract the readings.
Nearest cm	Look at the mm: 5 or more rounds up, less than 5 stays. 7 cm 5 mm is about 8 cm.
Scales and jugs	Find the unit. Count the gaps between two numbered marks and divide to find the step. Read the number below the pointer, then count on in steps.
Units	10 mm = 1 cm 100 cm = 1 m 1,000 m = 1 km 1,000 g = 1 kg 1,000 ml = 1 l.
Converting	Big unit to small unit: multiply (3 m = 300 cm). Small unit to big unit: divide (600 cm = 6 m).
Decimals of measures	2.5 m = 250 cm. 1.5 kg = 1,500 g. 0.25 l = 250 ml. 3 m 40 cm = 340 cm.
Comparing and ordering	Change to the same unit (the smaller one) first. 3 km = 3,000 m, which is more than 2,500 m.
Sensible units	1 cm is a fingernail, 1 m is a big step, 1 kg is a bag of sugar, 1 l is a big carton of juice. Choose the unit that gives a sensible number.
Adding and subtracting measures	Same units first. Use columns. 1 m 45 cm + 2 m 80 cm = 145 cm + 280 cm = 425 cm = 4 m 25 cm.
Multiplying and dividing measures	Work in the smaller unit. 4 × 350 ml = 1,400 ml = 1.4 l. 1 l ÷ 4 = 1,000 ml ÷ 4 = 250 ml.
Perimeter	The distance all the way round. Rectangle: 2 × (length + width). Square: 4 × side. Add ALL the sides.
Missing sides	You go right as far as you go left, and down as far as you go up. Work out the missing sides, then add all the sides.
Area	The number of squares inside a shape, in cm². Rectangle: rows × squares in each row. Split L-shapes into rectangles and add.
Area or perimeter?	Area is the space inside (cm²). Perimeter is the distance round the edge (cm). They are different, and a bigger perimeter does not always mean a bigger area.

Can you…?

I can read a ruler in cm and mm, and write a length in cm and mm, in mm, or as a decimal.
I can measure to the nearest cm and mm.
I can read weighing scales, jugs and other scales, and work out what each small mark is worth.
I can change between km and m, m and cm, cm and mm, kg and g, and l and ml.
I can use decimals like 2.5 m = 250 cm and 1.5 kg = 1,500 g.
I can compare and order measures in different units.
I can choose a sensible unit and make a sensible estimate.
I can add and subtract measures, and solve measure problems.
I can find the perimeter of squares, rectangles and L-shapes, including missing sides.
I can find the area of a shape by counting squares, and use rows and columns for rectangles.
I know that area and perimeter are different.

Key terms

Length: How long something is, measured in mm, cm, m or km.
Mass: How heavy something is, measured in g or kg.
Capacity: How much a container holds, measured in ml or l.
Millimetre (mm): A very small unit of length. 10 mm = 1 cm.
Centimetre (cm): A unit of length. 100 cm = 1 m.
Metre (m): A unit of length. 1,000 m = 1 km.
Kilometre (km): A unit for long distances. 1 km = 1,000 m.
Gram (g): A small unit of mass. 1,000 g = 1 kg.
Kilogram (kg): A unit of mass. 1 kg = 1,000 g.
Millilitre (ml): A small unit of capacity. 1,000 ml = 1 l.
Litre (l): A unit of capacity. 1 l = 1,000 ml.
Scale: A line of marks with numbers on it, like on a ruler, scales or a jug.
Step (interval): The amount between two small marks on a scale.
Convert: To change a measure from one unit to another.
Estimate: A sensible guess, or an answer found by rounding.
Perimeter: The distance all the way round the edge of a shape.
Rectilinear: Having straight sides that meet at right angles, like a rectangle or an L-shape.
Area: The amount of flat space inside a shape, measured in square units such as cm².
Square centimetre (cm²): The area of a square with sides of 1 cm.
Row and column: A row goes across. A column goes down.