Weight Problem Solving

I want the plan to focus on solving problems involving weight

Create a success criteria for this lesson

Create a high engaging introduction and a range of questioning for this maths lesson Identify common misconceptions and areas of difficulty for solving problems involving weight

Create use of targeted whole class questions- Questions shouldn't just ask for the correct answer they should require pupils to explain their thinking justifying their reasoning. (Use Bloom's taxonomy to help create questions beyond basic thinking and encourage deeper thinking)

Create an example for children to copy into books and use to support work

Include AfL points throughout teaching and modelling stage ( tell me What AfL to use, where to use it?) Modelling

Plan a task that gradually increases in complexity, e.g. by adding more elements pupils need to think about or having them apply what they have been taught to different situations.

plenary

Align with White Rose Maths Scheme

National Curriculum Links

Mathematics - Year 4 - Measurement:
- Convert between different units of measure (e.g. kilogram to gram).
- Solve simple problems involving mass and capacity, including using decimals and fractions.
- Use knowledge of place value, multiplication, and division to solve measurement problems.

Learning Objectives

By the end of the lesson, pupils will be able to:

Convert between kilograms and grams fluently.
Solve increasingly complex word problems involving weights.
Explain and justify their reasoning when solving weight problems.
Apply problem-solving strategies to real-world mass measurements.

Success Criteria

I can convert kilograms to grams and grams to kilograms accurately.
I can read and understand word problems involving weight.
I can choose the correct method to solve weight problems.
I can explain my thinking clearly and justify my answers.
I can check my answers for accuracy.

Resources

Whiteboard and pens
Individual dry-wipe boards and pens for students
Weight conversion chart (kg/grams)
Printed worksheets with structured problems
Real-life objects (e.g. bags of sugar, weights) for demonstration
Place value counters or number lines (optional)

Introduction (10 minutes)

Engaging Starter (Hook):

Begin by holding up two bags: one labelled 1 kilogram of sugar and another labelled 500 grams. Ask the class:

“Which bag is heavier?”
“How many grams do you think are in 1 kilogram?” (Elicit answers, guide towards 1000 grams)
Demonstrate converting 1 kg into 1000 g using the weight conversion chart on the board.
Show a quick visual (e.g. 1000g = 1kg) to emphasise the relationship.

Targeted Questions (use Bloom’s Taxonomy):

Remembering: How many grams are there in 1 kilogram?
Understanding: Why do you think we need to convert kilograms to grams?
Applying: If a packet weighs 3kg, how many grams is that?
Analysing: If 700 grams is less than 1 kilogram, how many grams would make 1kg?
Evaluating: How can we check if our conversion is correct?
Creating: Can you think of other real-life examples where you might need to convert kilograms and grams?

Modelling & Teaching (15 minutes)

Display and copy the example on the board for pupils to copy into their books:

Example: A watermelon weighs 2 kilograms and 350 grams. An orange weighs 650 grams. How much do they weigh altogether?

Step 1: Convert 2 kilograms to grams:
2 kg = 2 × 1000 = 2000 g

Step 2: Add the extra grams of the watermelon:
2000 g + 350 g = 2350 g

Step 3: Add the weight of the orange:
2350 g + 650 g = 3000 g

Step 4: Convert back to kilograms:
3000 g ÷ 1000 = 3 kg

Answer: The total weight is 3 kilograms.

AfL Checkpoint 1 (After Step 2)

Ask pupils to explain why we need to convert kilograms into grams before adding the weights. Request three volunteers to justify their thinking in detail.

Guided Practice (15 minutes)

Activity: Graduated Weight Problems

Pupils work in pairs or small groups on these problems on mini whiteboards:

Basic: Convert 5 kg to grams and add 750 g.
Moderate: A bag of rice weighs 1.2 kg and a tin of beans weighs 850 g. What is their total weight in kilograms and grams?
Complex: Lucy bought 3 bags of flour weighing 1.5 kg each and 2 bags of sugar weighing 2.25 kg each. What is the total weight of all the bags in grams?

Targeted Whole Class Questions (for the teacher to ask during activity):

How did you decide whether to convert kilograms into grams or grams into kilograms first? Can you explain your reasoning?
When adding weights together, what strategy helps you keep the numbers organised?
Can someone explain why it’s sometimes easier to convert everything to grams first?
What could be confusing in a weight problem, and how do you avoid that?
How can breaking down the problem into smaller parts help you?

AfL Checkpoint 2 (During activity)

Circulate and ask pupils to explain aloud the step they are on and why.
Use mini whiteboards for quick spot-checks of conversions and calculations.

Common Misconceptions and Difficulties

Pupils confusing grams and kilograms and not converting properly before adding or subtracting.
Adding units without converting, e.g., adding 2 kg + 500 directly without conversion.
Forgetting to convert back to kilograms when final answers exceed 1000 grams.
Misreading word problems by missing key information such as mixed units or extra grams.
Difficulty with place value during conversion (e.g., misunderstanding 2.5 kg = 2500 g vs. 250 g).

Plenary (5 minutes)

Review & Reflect

Ask several pupils to share one interesting thing they learned today.
Pose a challenge question:
“If the total weight of a box is 4.8 kilograms, and part of the weight is 2.75 kilograms, how much does the other part weigh? Explain how you worked it out.”

Self-Assessment Tick:

Pupils tick against the success criteria what they think they did well.

Extension Ideas (Homework or for Higher Attainers)

Write their own weight problem involving kilograms and grams.
Solve problems involving averaging weights or finding the difference between multiple weights.

Links to White Rose Maths Scheme

This lesson fully aligns with White Rose Year 4 Measurement block:

Week 9 - Measure: Mass and Capacity
Utilises concrete-pictorial-abstract model with contextualised real-world problems.
Emphasises fluency in converting kg and g, supported by problem solving and reasoning.

This lesson plan ensures pupils develop mathematical fluency, reasoning, and problem-solving skills aligned to the National Curriculum requirements, using engaging, real-life contexts and effective formative assessment.

Teaching Instructions