Year 3 Maths Worksheet: Adding and Subtracting Mass Using Part-Whole Models

Let’s solve each part step by step.

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Part 1: Amir’s method — adding masses by separating kg and g

Amir adds kilograms together and grams together, then combines them.

Example given:
> 1 kg and 500 g + 2 kg and 200 g
→ (1 kg + 2 kg) = 3 kg
→ (500 g + 200 g) = 700 g
→ Total = 3 kg and 700 g

So we fill the box with: 3 kg and 700 g

Also, the top-right circle should be the total mass: 3 kg 700 g → but since it's split into two circles for kg and g, the top circle is just the sum of the two bottom ones? Wait — looking at the diagram:

Left side:
Top circle: 3 kg → from 1 kg + 2 kg
Right side: Top circle should be 500 g + 200 g = 700 g

But in the diagram, the right-top circle is empty — so we write 700 g there.

Actually, re-reading: “He partitions each mass into kilograms and grams and calculates them separately.”

So for the first example:

Left tree: 3 kg ← from 1 kg + 2 kg
Right tree: ? ← from 500 g + 200 g → that’s 700 g

So the top-right circle is 700 g

And the final answer box below is: 3 kg and 700 g

✔ So for the first problem:

Top-right circle: 700 g
Bottom box: 3 kg and 700 g

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Now use Amir’s method for the next four problems.

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Problem A: 2 kg and 300 g + 3 kg and 400 g

Kg: 2 + 3 = 5 kg
g: 300 + 400 = 700 g
Total: 5 kg and 700 g

Top-left circle: 5 kg
Top-right circle: 700 g
Box: 5 kg and 700 g

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Problem B: 4 kg and 100 g + 1 kg and 800 g

Kg: 4 + 1 = 5 kg
g: 100 + 800 = 900 g
Total: 5 kg and 900 g

Top-left circle: 5 kg
Top-right circle: 900 g
Box: 5 kg and 900 g

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Problem C: 1 kg and 600 g + 2 kg and 100 g

Wait — look at the diagram: it says “1 kg and 600 g + 2 kg and 100 g” but under the trees, the grams are labeled as 600 g and 300 g? That must be a typo in the worksheet? Or did I misread?

Looking again:

The text says:
“1 kg and 600 g + 2 kg and 100 g”

But in the diagram, the right-side gram circle says 300 g, not 100 g.

That’s inconsistent. But since the instruction is to use Amir’s method on the numbers shown in the diagram, we go by what’s drawn.

In the diagram for this problem:

Left: 1 kg and 600 g
Right: 2 kg and 300 g ← even though text says 100 g, the picture shows 300 g.

This is likely a printing error. But since the student is to follow the diagram, we’ll use 300 g.

So:

Kg: 1 + 2 = 3 kg
g: 600 + 300 = 900 g
Total: 3 kg and 900 g

Top-left circle: 3 kg
Top-right circle: 900 g
Box: 3 kg and 900 g

*(Note: If the text was correct and it’s 100 g, then 600+100=700g → 3kg 700g. But diagram shows 300g. We’ll go with diagram since it’s visual task.)*

Actually — let me double-check the original image description.

User wrote:
"1 kg and 600 g + 2 kg and 100 g"
but in the diagram:
left: 1 kg, 600 g
right: 2 kg, 300 g

Yes — mismatch. Since the worksheet has both text and diagram, and the diagram is part of the model, perhaps it’s intentional? Or mistake?

To be safe, let’s assume the diagram is correct because the student is filling boxes based on the trees shown.

So we proceed with 300 g.

Answer: 3 kg and 900 g

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Problem D: 3 kg and 200 g + 4 kg and 200 g

Kg: 3 + 4 = 7 kg
g: 200 + 200 = 400 g
Total: 7 kg and 400 g

Top-left circle: 7 kg
Top-right circle: 400 g
Box: 7 kg and 400 g

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Next: Jar of cookies

Jar with cookies: 900 g
Empty jar: 300 g
Cookies only: 900 - 300 = 600 g

Box: 600 g

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Last section: Choose appropriate approach

These involve mixed units or fractions.

First:
5 kg – 3½ kg

Convert to same unit or subtract directly.

5 - 3.5 = 1.5 kg → which is 1½ kg

Or: 5 kg = 4 kg + 1 kg = 4 kg + 1000 g
3½ kg = 3 kg + 500 g
Subtract: (4-3) kg + (1000-500) g = 1 kg 500 g = 1½ kg

Same thing.

Answer: 1½ kg

Second:
2 kg and 400 g + 4½ kg

Break down 4½ kg = 4 kg + 500 g

Add kg: 2 + 4 = 6 kg
Add g: 400 + 500 = 900 g
Total: 6 kg and 900 g

Alternatively, convert all to kg:

2 kg 400 g = 2.4 kg
4.5 kg
Sum: 2.4 + 4.5 = 6.9 kg = 6 kg 900 g

Answer: 6 kg and 900 g

Third:
3 kg + 1½ kg – 2 kg

Do step by step:

3 + 1.5 = 4.5 kg
4.5 - 2 = 2.5 kg = 2½ kg

Or:

3 kg + 1 kg 500 g = 4 kg 500 g
Minus 2 kg = 2 kg 500 g = 2½ kg

Answer: 2½ kg

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Now compile all answers.

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Final Answer:

First example (top):
Top-right circle: 700 g
Box: 3 kg and 700 g

Problem A (2kg300g + 3kg400g):
Top-left: 5 kg
Top-right: 700 g
Box: 5 kg and 700 g

Problem B (4kg100g + 1kg800g):
Top-left: 5 kg
Top-right: 900 g
Box: 5 kg and 900 g

Problem C (1kg600g + 2kg300g [as per diagram]):
Top-left: 3 kg
Top-right: 900 g
Box: 3 kg and 900 g

Problem D (3kg200g + 4kg200g):
Top-left: 7 kg
Top-right: 400 g
Box: 7 kg and 400 g

Jar of cookies:
Box: 600 g

Fraction problems:

5 kg – 3½ kg = 1½ kg
2 kg 400 g + 4½ kg = 6 kg and 900 g
3 kg + 1½ kg – 2 kg = 2½ kg

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Final Answer:
700 g; 3 kg and 700 g; 5 kg; 700 g; 5 kg and 700 g; 5 kg; 900 g; 5 kg and 900 g; 3 kg; 900 g; 3 kg and 900 g; 7 kg; 400 g; 7 kg and 400 g; 600 g; 1½ kg; 6 kg and 900 g; 2½ kg