Grade 2 · Repeat equal measuring units · 269 of 750
Repeat equal measuring units: equal units laid end to end: 2; length of each unit: 4 cm
A measuring strip for a classroom activity is assembled from 2 equal pieces, each 4 cm long. Find the length of the original strip 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 measuring strip for a classroom activity is assembled from 2 equal pieces, each 4 cm long. First find the length of the original strip in centimetres. Then answer: How long would a strip made from one more identical piece be?
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A starting point
Measurement repeats a fixed unit end to end. No gaps or overlaps are allowed, and the zero mark must align with the starting endpoint.
Work through the reasoning
Step 1
Identify the quantities and the task
A measuring strip for a classroom activity is assembled from 2 equal pieces, each 4 cm long. The first task is to find the length of the original strip in centimetres. Measurement repeats a fixed unit end to end. No gaps or overlaps are allowed, and the zero mark must align with the starting endpoint.
Step 2
Calculate the original result
2 × 4 cm = 8 cm. The 2 pieces span 8 cm; the number of pieces and the number of centimetres differ when a piece is longer than one centimetre.
Step 3
Complete the follow-up calculation
How long would a strip made from one more identical piece be? 12 cm. One additional piece contributes 4 cm.
The answer
2 × 4 cm = 8 cm. The 2 pieces span 8 cm; the number of pieces and the number of centimetres differ when a piece is longer than one centimetre. Follow-up: 12 cm. One additional piece contributes 4 cm.
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 measuring strip for a classroom activity is assembled from 2 equal pieces, each 4 cm long. Measurement repeats a fixed unit end to end. No gaps or overlaps are allowed, and the zero mark must align with the starting endpoint. The 2 pieces span 8 cm; the number of pieces and the number of centimetres differ when a piece is longer than one centimetre.
2 × 4 cm = 8 cm
03 · Reflect and transfer
Explain what changes and why.
Add one measuring piece at a time. Each piece extends the total by the same length, so the endpoint records repeated addition. 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.