Year 5 - Maths
Multiply 1-digit numbers by decimal fractions using written methods
Calculating with decimal fractions
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will explain the effect of multiplying and dividing a number by 10, 100 and 1,000 and use their knowledge of multiplying decimal fractions by whole numbers to solve measures problems.
Lesson Summary
You will learn to explain how to multiply 1-digit numbers by decimal fractions using written methods.
Key Notes
- Use scaling to convert the decimal fraction to a whole number then multiply; use scaling to adjust the product.
- If using short multiplication with decimal fractions, align the decimal point in the decimal fraction and product.
Vocabulary To Learn
- Estimation: When we estimate, we find a value that is close enough to the right answer, usually with some thought or calculation involved.
- Scaling: Scaling is when a given quantity is made ___ times the size. It can be used to adjust the size of a factor. In this lesson, scaling will involve making values 10 or 100 times the size.
Common Mistakes To Avoid
- The short multiplication algorithm may not be correctly aligned.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Use scaling to convert the decimal fraction to a whole number then multiply; use scaling to adjust the product. If using short multiplication with decimal fractions, align the decimal point in the decimal fraction and product.
2. Use this key word in a maths sentence and explain it clearly. 'Estimation'
When we estimate, we find a value that is close enough to the right answer, usually with some thought or calculation involved. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: The short multiplication algorithm may not be correctly aligned. Correction: Check that the decimal point aligns in the decimal fraction and the product. Scaffolding with place value columns may support further.
More Lessons In This Unit
- Converting units of length Study Guide
- Converting units of mass and capacity Study Guide
- Divide decimal fractions by 1-digit numbers Study Guide
- Divide decimal fractions by 1-digit numbers using written methods Study Guide
- Explain how to multiply and divide a number by 10, 100 and 1,000 Study Guide
- Multiply 1-digit numbers by decimals Study Guide
- Multiply hundredths by whole numbers Study Guide
- Multiply tenths by whole numbers Study Guide
- Multiplying and dividing a number by 10, 100 and 1,000 Study Guide
- Multiplying and dividing a number by 10, 100 and 1,000 including bridging 1 Study Guide
- Predicting the size of a product Study Guide
- Solve measures problems using knowledge of multiplying decimal fractions Study Guide
- The relationship between multiplying by 0.01 and dividing by 100 Study Guide
- The relationship between multiplying by 0.1 and dividing by 10 Study Guide
Browse all guides in the Year 5 Maths guide library.