Grade 4 · Combine metres with extra centimetres · 421 of 750
Combine metres with extra centimetres: whole metres: 4; extra centimetres: 49
A measurement for a classroom activity consists of 4 whole metres and 49 extra centimetres. Find the full measurement in centimetres, explain the calculation, and check a related question.
Try the question, use a hint when you need one, and compare your reasoning with the worked solution. The animation starts with this chapter’s values; changing its controls explores a new case.
01 · Make a prediction
Your practice question
A measurement for a classroom activity consists of 4 whole metres and 49 extra centimetres. First find the full measurement in centimetres. Then answer: What is the measurement entirely in centimetres?
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A starting point
One of the larger units contains 100 of the smaller units. Convert the whole-unit part first, then add the extra part in the same unit; do not add differently sized units as if they were identical.
Work through the reasoning
Step 1
Identify the quantities and the task
A measurement for a classroom activity consists of 4 whole metres and 49 extra centimetres. The first task is to find the full measurement in centimetres. One of the larger units contains 100 of the smaller units. Convert the whole-unit part first, then add the extra part in the same unit; do not add differently sized units as if they were identical.
Step 2
Calculate the original result
4 × 100 + 49 = 449 centimetres. The total is 449 centimetres, or 4.49 metres. Both names refer to the same measurement.
Step 3
Complete the follow-up calculation
What is the measurement entirely in centimetres? 449 centimetres: 400 from the whole metres, plus 49 extra.
The answer
4 × 100 + 49 = 449 centimetres. The total is 449 centimetres, or 4.49 metres. Both names refer to the same measurement. Follow-up: 449 centimetres: 400 from the whole metres, plus 49 extra.
Compare the method as well as the result. A different valid method may reach the same answer. Keep exact values until the last step when the question asks for rounding.
02 · Explore the model
See the mathematical relationship move.
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Watch the relationship
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The mathematical idea
A measurement for a classroom activity consists of 4 whole metres and 49 extra centimetres. One of the larger units contains 100 of the smaller units. Convert the whole-unit part first, then add the extra part in the same unit; do not add differently sized units as if they were identical. The total is 449 centimetres, or 4.49 metres. Both names refer to the same measurement.
4 × 100 + 49 = 449 centimetres
03 · Reflect and transfer
Explain what changes and why.
Follow the conversion from the larger-unit part to its smaller-unit equivalent, then combine the extra smaller units. Explain which quantity changes and which relationship stays valid. Use the starting values again before checking your written answer.
This is a distinct guided scenario using a reusable mathematical model. Similar-looking diagrams can represent different given values and conclusions; they are not different mathematical theories.