Relationship Between Volume, Capacity and Mass
Primary 6 · Mathematics
Relationship Between Volume, Capacity and Mass
Lesson 2 of 5
15 min
Let's begin
At the market, Gatete buys 2 kg of rice, 750 g of sugar and a 500 g packet of salt. His bag can carry at most 3 kg. Will it hold all his shopping, or will the bag tear on the way home?
The mass of an object tells you how heavy it is. We measure it in kilograms (kg) and grams (g). A bag of sugar might be 1 kg. A pen is about 10 g. Very heavy loads, like a lorry of sand, are measured in tonnes (t): 1 t = 1 000 kg.
| kg | hg | dag | g | dg | cg | mg |
|---|---|---|---|---|---|---|
| kilogram | hectogram | decagram | gram | decigram | centigram | milligram |
It works just like capacity: bigger unit to smaller unit, multiply; smaller to bigger, divide.
Worked examples
3.6 kg = 3.6 × 1 000 = 3 600 g.
2 450 g = 2 450 ÷ 1 000 = 2.45 kg.
7 hg = 7 × 100 = 700 g = 0.7 kg.
13.6 dag = 13.6 × 10 = 136 g = 0.136 kg.
2.5 t = 2.5 × 1 000 = 2 500 kg.
A place-value table helps with the small units. 4.536 kg = 4 536 g, which is 4 kg 5 hg 3 dag 6 g, one digit in each column.
Change everything into grams: 2 kg = 2 000 g.
Total = 2 000 + 750 + 500 = 3 250 g = 3.25 kg.
3.25 kg is more than 3 kg, so the bag is 250 g too weak. He should carry the salt in his hand.
Which is heavier, 1.2 kg or 1 050 g? Write both in grams: 1.2 kg = 1 200 g. Since 1 200 g is more than 1 050 g, 1.2 kg is heavier.
Worked example
A lorry can carry 5 t. It is loaded with 80 bags of cement of 50 kg each. How many more bags can it take?
Load = 80 × 50 = 4 000 kg = 4 t. It can take 5 000 − 4 000 = 1 000 kg more, and 1 000 ÷ 50 = 20 more bags.
Tip
Remember the order of the mass units with a sentence: Keza Has Done Good Deeds, Cheering Mum: kg, hg, dag, g, dg, cg, mg. Each step is × 10.
Answers
What you learned today
Sources and credits
Quick check
Change 3 250 g into kilograms.
