Free Grade 3 Adding Decimals Lessons
Free Grade 3 lessons for Adding Decimals: 12 real questions with a full answer key and worked solutions. Decimals extend place value past the ones: tenths, hundredths, thousandths. Line up decimal points when adding or subtracting.
Free
Foundation
35 min
24
Learning objectives
Every objective is checkable, and each one maps to an activity and an assessment.
- RememberIdentify adding decimals
Identify adding decimals accurately in a familiar context.
Assessed by: Exit ticket of four short items
- UnderstandExplain adding decimals
Explain adding decimals accurately in a familiar context.
Assessed by: Exit ticket of four short items
- ApplyCalculate adding decimals
Calculate adding decimals accurately in a familiar context.
Assessed by: Exit ticket of four short items
- AnalyseCompare adding decimals
Compare adding decimals 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 Adding Decimals works
Decimals extend place value past the ones: tenths, hundredths, thousandths. Line up decimal points when adding or subtracting.
12 practice questions
Easy to hard, 24 marks in total. Try them first, then open the answers.
- 1.27.9 + 82.4 = ?[1]
- 2.60.7 + 98 = ?[1]
- 3.70.5 + 78.9 = ?[1]
- 4.81.5 + 76.4 = ?[1]
- 5.8.66 − 7.08 = ?[2]
- 6.7.28 + 1.14 = ?[2]
- 7.2.84 − 2.23 = ?[2]
- 8.3.94 + 8.34 = ?[2]
- 9.0.756 × 8 = ?[3]
- 10.0.187 × 6 = ?[3]
- 11.0.392 × 9 = ?[3]
- 12.0.216 × 9 = ?[3]
Show answers and working
1. 110.3
Line up the decimal points. Fill gaps with zeros so both have 1 decimal place. Add as whole numbers: 110.3.
2. 158.7
Line up the decimal points. Fill gaps with zeros so both have 1 decimal place. Add as whole numbers: 158.7.
3. 149.4
Line up the decimal points. Fill gaps with zeros so both have 1 decimal place. Add as whole numbers: 149.4.
4. 157.9
Line up the decimal points. Fill gaps with zeros so both have 1 decimal place. Add as whole numbers: 157.9.
5. 1.58
Line up the decimal points. Fill gaps with zeros so both have 2 decimal places. Subtract as whole numbers: 1.58.
6. 8.42
Line up the decimal points. Fill gaps with zeros so both have 2 decimal places. Add as whole numbers: 8.42.
7. 0.61
Line up the decimal points. Fill gaps with zeros so both have 2 decimal places. Subtract as whole numbers: 0.61.
8. 12.28
Line up the decimal points. Fill gaps with zeros so both have 2 decimal places. Add as whole numbers: 12.28.
9. 6.048
Ignore the decimal: 756 × 8 = 6048. Put back 3 decimal places: 6.048.
10. 1.122
Ignore the decimal: 187 × 6 = 1122. Put back 3 decimal places: 1.122.
11. 3.528
Ignore the decimal: 392 × 9 = 3528. Put back 3 decimal places: 3.528.
12. 1.944
Ignore the decimal: 216 × 9 = 1944. Put back 3 decimal places: 1.944.
Worked examples
43.3 + 88.9 = ?
- Line up the decimal points.
- Fill gaps with zeros so both have 1 decimal place.
- Add as whole numbers: 132.2.
- Answer: 132.2
3.51 + 3.59 = ?
- Line up the decimal points.
- Fill gaps with zeros so both have 2 decimal places.
- Add as whole numbers: 7.1.
- Answer: 7.1
0.208 × 8 = ?
- Ignore the decimal: 208 × 8 = 1664.
- Put back 3 decimal places: 1.664.
- Answer: 1.664
Interactive practice
Free, no account required — answer on screen or print it.
Common mistakes
What learners typically get wrong, and how to fix it.
Thinks 0.25 is bigger than 0.3 because 25 > 3.
Correction: Fill with zeros: 0.25 vs 0.30.
Lines up the last digits instead of the decimal points.
Correction: Decimal points go in one straight column.
Teacher tips
- · Use money to make tenths and hundredths concrete.
Parent tips
- · Add up prices with cents together.
Real-life applications
- · Money, measurements, race times.
Assessment objectives
How mastery is evidenced, and which standards it maps to.
Every free resource for Adding Decimals
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Frequently asked
- Is this Grade 3 Adding Decimals 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 Rounding Decimals, Comparing Decimals, Fractions. 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 Adding Decimals?
- Move on to Multiplying Decimals, Dividing Decimals, Recurring Decimals, Whole Numbers, which build directly on this idea.
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