Checking and securing understanding of rounding and truncating
Lesson details
Learning outcome
I can estimate a value by rounding or truncating to a given degree of accuracy.
Key learning points
- The first significant figure is the first non-zero digit to have place value.
- Truncation does not consider the digits that follow in the value.
- The loss of accuracy through rounding is not always bad.
Keywords
Round - Rounding means to change a number into another number that is approximately the same value but is easier to work with.
Degree of accuracy - A degree of accuracy shows how precise a number or measurement is. E.g to the nearest cm, nearest 10, 1 s.f., etc.
Significant figures - Significant figures are the digits in a number that contribute to the accuracy of the number. The first significant figure is the first non-zero digit.
Truncation - Truncation is when we simplifying a number by 'cutting off' one or more of the digits and replacing them with zeros if necessary to preserve place value.
Common misconception
When truncating, pupils are tempted to round. Also, when truncating, they cut off the number without thinking about the magnitude.
The use of the place value table shows the magnitude of the number, thus preserving their place value when truncating.
Teacher tip
As a challenge ask pupils if any of the questions could have been changed without changing the numbers used or found on task A question 1. E.g. (e) could also have been round 3971.12 to the nearest hundred.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Aisha writes 2684 as approximately 3000. Aisha has written it to the nearest .
Q2.Which digit is in the ten thousands column in 742 683?
Q3.Which digit is in the hundredths column in 129.083?
Q4.In the number 3 547 028, which column is the digit 5 in?
Q5.In the number 123.4567, which column is the 6 in?
Q6.Round each number to the nearest 10.
Assessment exit quiz
6 Questions
Q1.Truncation is when we simplifying a number by 'cutting off' one or more of the digits and replacing them with if necessary to preserve place value.
Q2.The mass of an elephant is 5000 kg when given to the nearest 1000 kg. Which of the following would not be the mass of an elephant?
Q3.Round 345 678 to the nearest ten thousand.
Q4.Round 15.0872 to 1 decimal place.
Q5.Round each of the following to 2 significant figures.
Q6.Which of the following do not give the same answer when rounded to 2 significant figures or truncated to 2 significant figures?
To help you plan your 10 maths lesson on: Checking and securing understanding of rounding and truncating, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 maths lesson on: Checking and securing understanding of rounding and truncating, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 maths lessons from the Rounding, estimation and bounds unit, dive into the full secondary maths curriculum, or learn more about lesson planning.