3.2 Rounding · Unit 3 Place value and rounding

1 · Teaching slidesuse ← → keys

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2 · Key words

roundTo replace a number by a nearby, simpler one.

degree of accuracyHow precise an answer needs to be, such as “to 2 decimal places”.

decimal placeA digit position after the decimal point.

significant figuresThe digits that carry meaning, counted from the first non-zero digit.

3 · Summary of the sectionrevise from this

The method is the same for every degree of accuracy.
Find the digit in the rounding position, then look at the digit immediately to its right.
If that digit is 5 or more, increase the rounding digit by 1.
If it is less than 5, leave the rounding digit as it is.
Then drop everything after the rounding position.
Rounding up can carry: 9.999 to 2 d.p. is 10.
For a division, work out one more decimal place than you need, then round.
Round once, from the original number — rounding in stages can give the wrong answer.

PDFPrintable worksheet All 56 questions, space to work PDFWorked answers Full solutions, not just the answer

Video lessons4 videos

Math Antics - Rounding

American mathantics

Builds the rounding rule from the number line, so it makes sense rather than being a recipe.

How to Round Decimals

American Math with Mr. J

Rounding to a given number of decimal places, step by step.

Rounding to 1 Decimal Place

British MatholiaChannel

A short, focused treatment of the commonest case.

Rounding Decimals to Significant Figures

British stretchMaths Tutor Tom

Significant figures, which Stage 7 meets alongside decimal places.

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Rounding