Primary 2 maths · Measurement & time · About 8 minutes
Measure and compare mass in grams and kilograms
Look at the scale. Say grams or kilograms with the number.
Start the interactive lesson →Related practice: Measure match
What you will learn
- Measure and compare mass in grams and kilograms
Models used: number sentences, stories, bar models.
Before you start
Compare masses in the same unit
Two packets have masses of 300 g and 500 g. Which is heavier?
Both bars use the same scale. Compare their lengths and read the names beside them.
Read the unit with each number. Both measurements use the same unit, so their numbers can be compared.
Both bars use the same scale. Compare their lengths and read the names beside them.
500 g is the greater measurement. The longer bar represents the larger amount, not a drawing of the object’s shape.
500 > 300
Both bars use the same scale. Compare their lengths and read the names beside them.
Grams suit light objects; kilograms suit heavier ones. Keep the unit beside the reading.
500 − 300 = 200 g
What did the picture help us see?
Grams suit light objects; kilograms suit heavier ones. Keep the unit beside the reading.
Worked example: A new example, together
One bag measures 7 kg and another 9 kg. What is the difference?
Both bars use the same scale. Compare their lengths and read the names beside them.
Look at the scale. Say grams or kilograms with the number.
Comparing measurements requires matching the amount and unit.
Both bars use the same scale. Compare their lengths and read the names beside them.
Both measurements use the same unit.
One bag measures 7 kg and another 9 kg. What is the difference?
2 kg
Both bars use the same scale. Compare their lengths and read the names beside them.
9 − 7 = 2.
Both bars use the same scale. Compare their lengths and read the names beside them.
The difference is 2 kg.
Both bars use the same scale. Compare their lengths and read the names beside them.
Check the result against the question we started with.
Re-read the labels and unit before comparing the numbers.
We found 2 kg. Comparing measurements requires matching the amount and unit.
Common mistakes to discuss
- Comparing numbers across different units. Change both amounts to the same unit before comparing. 700 g is less than 1 kg, although 700 is the larger number.
Check your understanding
- Measure and compare mass in grams and kilograms
- read a mass measurement
- check the answer against the original quantities and units
Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.
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