lesson
Keep decimal places aligned
1 · Learn
To round 6.47 to one decimal place, compare 6.4 and 6.5. The midpoint is 6.45, so choose 6.5. To the nearest whole, 6.47 rounds to 6.
In decimal addition and subtraction, line up decimal points so matching places align. You may add trailing zeros without changing value: 4.6 = 4.600.
2 · Worked example
I add 2.36 and 0.485 as 2.360 + 0.485 = 2.845. I do not align only the final digits.
3 · Your turn
Calculate 5.2 − 1.375. Round 8.64 to the nearest whole and to one decimal place.
Check your answer
3.825; 9; 8.6.
4 · Apply your learning
Estimate before calculating, then check with an inverse. Explain the precision required in a measurement context.
Adult guidance and safety
Model the calculation or measurement before relying on a procedure. Explain estimates, units and checks. Use a ruler/protractor and suitable diagrams where needed; text examples alone do not establish practical skill or fluency.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
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