Free Grade 3 Imaginary Unit Lessons
Free Grade 3 lessons for Imaginary Unit: 12 real questions with a full answer key and worked solutions. Metric units change by powers of 10: 10 mm in a cm, 100 cm in a m, 1000 m in a km. Multiply to convert to a smaller unit, divide to convert to a bigger one.
Free
Core
30 min
24
Learning objectives
Every objective is checkable, and each one maps to an activity and an assessment.
- UnderstandExplain imaginary unit
Explain imaginary unit accurately in a familiar context.
Assessed by: Exit ticket of four short items
- ApplyCalculate imaginary unit
Calculate imaginary unit accurately in a familiar context.
Assessed by: Exit ticket of four short items
- AnalyseCompare imaginary unit
Compare imaginary unit accurately in a familiar context.
Assessed by: Exit ticket of four short items
- EvaluateJustify imaginary unit
Justify imaginary unit accurately in a familiar context.
Assessed by: Exit ticket of four short items
Prerequisites
Close these gaps first — each has its own free lesson, worksheet and quiz.
How Imaginary Unit works
Metric units change by powers of 10: 10 mm in a cm, 100 cm in a m, 1000 m in a km. Multiply to convert to a smaller unit, divide to convert to a bigger one.
12 practice questions
Easy to hard, 24 marks in total. Try them first, then open the answers.
- 1.Convert 4 km to m.[1]
- 2.Convert 9 kg to g.[1]
- 3.Convert 6 cm to mm.[1]
- 4.Convert 8 kg to g.[1]
- 5.Convert 2.8 m to cm.[2]
- 6.Convert 4.6 km to m.[2]
- 7.Convert 3.7 cm to mm.[2]
- 8.Convert 4.7 kg to g.[2]
- 9.Convert 9.7 kg to g.[3]
- 10.Convert 3.5 kg to g.[3]
- 11.Convert 2.7 cm to mm.[3]
- 12.Convert 4.9 L to mL.[3]
Show answers and working
1. 4000 m
1 km = 1000 m. 4 × 1000 = 4000 m.
2. 9000 g
1 kg = 1000 g. 9 × 1000 = 9000 g.
3. 60 mm
1 cm = 10 mm. 6 × 10 = 60 mm.
4. 8000 g
1 kg = 1000 g. 8 × 1000 = 8000 g.
5. 280 cm
1 m = 100 cm. 2.8 × 100 = 280 cm.
6. 4600 m
1 km = 1000 m. 4.6 × 1000 = 4600 m.
7. 37 mm
1 cm = 10 mm. 3.7 × 10 = 37 mm.
8. 4700 g
1 kg = 1000 g. 4.7 × 1000 = 4700 g.
9. 9700 g
1 kg = 1000 g. 9.7 × 1000 = 9700 g.
10. 3500 g
1 kg = 1000 g. 3.5 × 1000 = 3500 g.
11. 27 mm
1 cm = 10 mm. 2.7 × 10 = 27 mm.
12. 4900 mL
1 L = 1000 mL. 4.9 × 1000 = 4900 mL.
Worked examples
Convert 7 L to mL.
- 1 L = 1000 mL.
- 7 × 1000 = 7000 mL.
- Answer: 7000 mL
Convert 6.2 m to cm.
- 1 m = 100 cm.
- 6.2 × 100 = 620 cm.
- Answer: 620 cm
Convert 7 L to mL.
- 1 L = 1000 mL.
- 7 × 1000 = 7000 mL.
- Answer: 7000 mL
Interactive practice
Free, no account required — answer on screen or print it.
Common mistakes
What learners typically get wrong, and how to fix it.
Divides when converting to a smaller unit.
Correction: Smaller units mean more of them — multiply.
Uses 100 for every conversion.
Correction: Learn which pairs use 10, 100 or 1000.
Teacher tips
- · Keep a conversion staircase on the wall.
Parent tips
- · Weigh fruit at the shop and convert kg to g.
Real-life applications
- · Cooking, measuring height, reading road signs.
Assessment objectives
How mastery is evidenced, and which standards it maps to.
Every free resource for Imaginary Unit
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Practice — Build fluency.
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Frequently asked
- Is this Grade 3 Imaginary Unit lesson really free?
- Yes. Every lessons on FreeMathWorksheet is free to use, print and share — no account, no paywall and no watermark.
- What should a learner already know before this?
- Start with Real Numbers. Each one has its own free lesson, worksheet and quiz.
- How is the lesson sequenced?
- Recognition first, then understanding, application, reasoning and finally mastery — the same ladder used across every free resource on the platform.
- What comes next after Imaginary Unit?
- Move on to Argand Diagram, Complex Arithmetic, Modulus and Argument, Whole Numbers, which build directly on this idea.
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