Class 3 — Mathematics
Measurement: Length, Weight, Capacity, and Time
Class 3
- ✓By the end of this lesson students will be able to measure length using standard units like centimetre and metre.
- ✓By the end of this lesson students will be able to measure weight using standard units like gram and kilogram.
- ✓By the end of this lesson students will be able to measure capacity using standard units like millilitre and litre.
- ✓By the end of this lesson students will be able to read time from a clock to the nearest minute and understand basic time concepts.
- ✓By the end of this lesson students will be able to compare objects based on their length, weight, and capacity.
Key concepts
Length tells us how long an object is or the distance between two points. We can measure length using non-standard units (like handspan, footspan) or standard units. Standard units give us an exact measurement.
The standard units for measuring length are centimetre (cm) for shorter lengths and metre (m) for longer lengths. We know that 1 metre = 100 centimetres.
Weight tells us how heavy an object is. We can compare the weight of objects by lifting them or using a weighing balance. Standard units help us find the exact weight.
The standard units for measuring weight are gram (g) for lighter objects and kilogram (kg) for heavier objects. We know that 1 kilogram = 1000 grams.
Capacity tells us how much liquid a container can hold. For example, how much water a bottle can hold or how much milk a jug can hold. We can compare capacities or measure them using standard units.
The standard units for measuring capacity are millilitre (ml) for smaller quantities of liquid and litre (L) for larger quantities of liquid. We know that 1 litre = 1000 millilitres.
Time tells us when events happen and how long they last. We use clocks to read time in hours and minutes. A clock has two main hands: the shorter hour hand and the longer minute hand.
The minute hand completes one full round in 60 minutes, which is 1 hour. The hour hand moves from one number to the next in 1 hour. We read time as 'o'clock', 'half past', 'quarter past', and 'quarter to'.
Key facts to remember
- 1Length is measured in centimetres (cm) and metres (m). 1 m = 100 cm.
- 2Weight is measured in grams (g) and kilograms (kg). 1 kg = 1000 g.
- 3Capacity is measured in millilitres (ml) and litres (L). 1 L = 1000 ml.
- 4Time is read from a clock using hour and minute hands. 1 hour = 60 minutes.
- 5The minute hand moves 5 minutes for each number it passes on the clock face.
- 6There are 7 days in a week and 12 months in a year.
Worked examples
Example 1
Convert 3 metres into centimetres.
Answer
300 cm
Remember, 'm' stands for metre and 'cm' stands for centimetre.
Example 2
A bag of rice weighs 5 kg. How many grams is this?
Answer
5000 g
Always write the correct unit with your answer.
Example 3
What time is shown on a clock where the hour hand is just past 7 and the minute hand is pointing at 3?
Answer
7:15 or Quarter past 7
Each number on the clock face represents 5 minutes for the minute hand.
Common mistakes
- ✗Confusing the hour hand and minute hand while reading time.
- ✗Forgetting to write the correct unit (cm, m, g, kg, ml, L) with the measurement.
- ✗Incorrectly converting between units (e.g., thinking 1 m = 10 cm instead of 100 cm).
- ✗Not understanding that 'quarter past' means 15 minutes past and 'half past' means 30 minutes past.
- ✗Using non-standard units (like handspan) when standard units are required for exact measurement.
Exam tips
- ★Always look carefully at the units given in the question and the units required for the answer.
- ★Practice reading different times on a clock face, including 'o'clock', 'half past', 'quarter past', and 'quarter to'.
- ★Memorise the conversion facts: 1 m = 100 cm, 1 kg = 1000 g, 1 L = 1000 ml, 1 hour = 60 minutes.
- ★When solving word problems, identify what is being measured (length, weight, capacity, or time) first.
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