Key ideas
Reading a scale
1. Pick two labelled numbers next to each other.
2. Count the spaces between them, not the lines.
3. Each space = difference ÷ number of spaces.
4. Count on from the labelled number below the pointer.
Watch out
Not every scale goes up in 1s. A space might be worth 2, 5, 25, 0.1 or more.
Thermometers can go below zero, so read carefully either side of 0.
Converting units
Going from a bigger unit to a smaller one, multiply. Going from a smaller unit to a bigger one, divide.
Reading a scale
How much water is in the jug?(2 marks)
What is each space worth?Labels go up 200 ml at a timeThere are 4 spaces between labels200 ÷ 4 = 50 ml per space✓1
In plain EnglishLook at two labelled numbers next to each other, like 400 and 600. Count the spaces between them: there are 4. So each space is worth 200 ÷ 4 = 50 ml.
Count on.From 600: one more space600 + 50 = 650 ml✓2
In plain EnglishThe water level is one space above 600, so add one lot of 50.
⚠ A common mistake: counting the lines instead of the spaces. There are 3 small lines between 400 and 600 but 4 spaces.
What mass do the scales show?(2 marks)
What is each space worth?Labels go up 500 g at a time, with 5 spaces500 ÷ 5 = 100 g per space✓1
In plain EnglishBetween 1000 and 1500 there are 5 spaces, so each is worth 100 g.
Count on.1000 + 3 × 100 = 1300 g✓2
In plain EnglishThe needle is 3 spaces past 1000.
Scales with decimals
What temperature does the thermometer show?(2 marks)
What is each space worth?Labels go up 1°C at a time, with 10 spaces1 ÷ 10 = 0.1°C per space✓1
In plain EnglishBetween 37 and 38 there are 10 spaces, so each one is a tenth: 0.1°C.
Count on.37 + 4 × 0.1 = 37.4°C✓2
In plain EnglishThe red line stops 4 spaces above 37.
Converting length
Change 3.5 m into centimetres.(1 mark)
Bigger to smaller: multiply.3.5 × 100 = 350 cm✓1
In plain EnglishMetres are bigger than centimetres, so there will be more of them: multiply. There are 100 cm in 1 m.
Converting mass and capacity
Change 750 g into kilograms.(1 mark)
Smaller to bigger: divide.750 ÷ 1000 = 0.75 kg✓1
In plain EnglishGrams are smaller than kilograms, so there will be fewer kilograms: divide by 1000. Move each digit three places to the right.
Change 1.2 litres into millilitres.(1 mark)
Bigger to smaller: multiply.1.2 × 1000 = 1200 ml✓1
In plain EnglishThere are 1000 ml in a litre. Litres are bigger, so multiply.
Measuring in context
A recipe needs 1 litre of milk. How much more milk needs to go in the jug?(3 marks)
Read the jug.Labels go up 250 ml, with 5 spaces: 250 ÷ 5 = 50 mlThe jug shows 650 ml✓1
In plain EnglishWork out what each space is worth, then read the level.
Same units.1 litre = 1000 ml✓2
In plain EnglishYou can only take away when both amounts are in the same unit.
Take away.1000 − 650 = 350 ml✓3
In plain EnglishTake what is in the jug away from what the recipe needs.
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Your turn
Read each scale carefully: work out what one space is worth first. For conversions, decide whether to multiply or divide. Stuck? Tap Need a hint?