Teach Genie
Teach it back in your own words, spot gaps, and remember it better.
When a measurement has been rounded, the true value is not exactly the number written. Bounds tell us the smallest and largest values the measurement could be.
The lower bound is the smallest possible value, and the upper bound is the boundary before the value would round up. For a length of 28 cm to the nearest cm, the interval is 27.5≤l<28.527.5 \le l < 28.527.5≤l<28.5.
To find bounds, work out the rounding gap and halve it. Nearest cm gives a half-gap of 0.50.50.5, nearest 5 m gives 2.52.52.5, and correct to 2 decimal places gives 0.0050.0050.005.
Question 1
4 marksA rectangle has a length of 21 cm, to the nearest cm, and a width of 5.3 cm, to the nearest mm.
The lower bound is the [ ] possible value before rounding, while the upper bound is the largest boundary value.
Revision notes for Edexcel GCSE Maths Bounds. Open the guide for explanations and worked examples. Written against the Edexcel GCSE Maths (1MA1) specification, so the content matches what's examinable rather than general Maths background.
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A length is 58.058.058.0 cm correct to the nearest millimetre. Which interval shows the possible values of the length lll?
