Place Value, Rounding & Estimation — Year 7 Revision Notes
These notes cover decimal place value, multiplying and dividing by powers of 10, rounding, and using estimation to check answers — all at Year 7 (Stage 7) level.
Place value and powers of 10
Each digit has a value because of its position. In 3.47 the 4 is worth four tenths and the 7 is worth seven hundredths. Multiplying by 10 moves every digit one place to the left; dividing by 10 moves every digit one place to the right.
Key Facts & Formulas
- × 10 → digits move 1 place left
- ÷ 10 → digits move 1 place right
Tips
- Think of the digits moving, not the decimal point, to avoid mistakes.
- Multiplying by 100 moves digits two places, by 1000 three places.
Rounding
To round, look only at the digit immediately after the place you are rounding to. If it is 5 or more, round up; if it is 4 or less, round down. To round 4.482 to one decimal place, look at the 8 — it is 5 or more, so 4.482 rounds to 4.5.
Key Facts & Formulas
- 5 or more → round up
- 4 or less → round down
Tips
- Only look at the next digit — never round in two steps.
- Keep trailing zeros if they are needed to show the accuracy, e.g. 3.40.
Estimation
To estimate, round each number to 1 significant figure and then calculate. For example, 312 × 18 is approximately 300 × 20 = 6000. Use this to check whether a calculated answer is sensible.
Key Facts & Formulas
- Round each number to 1 s.f., then calculate
- 312 × 18 ≈ 300 × 20 = 6000
Tips
- Use the ≈ symbol to show you are estimating.
- If your real answer is far from your estimate, re-check your working.
Revision Checklist
- I can state the value of any digit in a decimal
- I can multiply and divide by 10, 100 and 1000
- I can round whole numbers and decimals correctly
- I can estimate an answer to check a calculation
Frequently Asked Questions
Do I round in stages?
No. Always look only at the single digit immediately after the rounding position. Rounding in stages gives the wrong answer.
Build strong foundations in Place Value, Rounding & Estimation
A free trial class with Teacher Rig helps your Year 7 child master Place Value, Rounding & Estimation now — so IGCSE Maths feels familiar, not frightening, later.
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