Year 5 - Maths
Explain how to multiply and divide a number by 10, 100 and 1,000
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 and divide a number by 10, 100 and 1,000.
Key Notes
- When you multiply by 10, 100 or 1,000, the digits move one, two or three places to the left respectively.
- When you divide by 10, 100 or 1,000, the digits move one, two or three places to the right respectively.
Vocabulary To Learn
- Tenth: One-tenth is one part in ten equal parts.
- Hundredth: One-hundredth is one part in one hundred equal parts.
- Thousandth: One-thousandth is one part in one thousand equal parts.
Common Mistakes To Avoid
- Children may 'add' a zero when multiplying or vice versa when dividing. Children may place a zero at the end of the decimal fraction when multiplying, or vice versa when dividing.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
When you multiply by 10, 100 or 1,000, the digits move one, two or three places to the left respectively. When you divide by 10, 100 or 1,000, the digits move one, two or three places to the right respectively.
2. Use this key word in a maths sentence and explain it clearly. 'Tenth'
One-tenth is one part in ten equal parts. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Children may 'add' a zero when multiplying or vice versa when dividing. Children may place a zero at the end of the decimal fraction when multiplying, or vice versa when dividing. Correction: When we 'add' zero, the value of the number does not change. When we multiply or divide by a power of 10, we need to move all the digits the appropriate spaces to the left/right even if this means bridging one and moving into the decimal places.
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
- Multiply 1-digit numbers by decimal fractions using written methods 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.