New
New
Year 10
Higher

Checking and securing understanding of rounding and truncating

I can estimate a value by rounding or truncating to a given degree of accuracy.

New
New
Year 10
Higher

Checking and securing understanding of rounding and truncating

I can estimate a value by rounding or truncating to a given degree of accuracy.

Lesson details

Key learning points

  1. The first significant figure is the first non-zero digit to have place value.
  2. Truncation does not consider the digits that follow in the value.
  3. The loss of accuracy through rounding is not always bad.

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.

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.

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.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Aisha writes 2684 as approximately 3000. Aisha has written it to the nearest .
Correct Answer: thousand, 1000
Q2.
Which digit is in the ten thousands column in 742 683?
Correct Answer: 4, four
Q3.
Which digit is in the hundredths column in 129.083?
Correct Answer: 8, eight
Q4.
In the number 3 547 028, which column is the digit 5 in?
ten millions
millions
Correct answer: hundred thousands
ten thousands
thousands
Q5.
In the number 123.4567, which column is the 6 in?
hundred thousandths
ten thousandths
Correct answer: thousandths
tenths
thousands
Q6.
Round each number to the nearest 10.
Correct Answer:45,50

50

Correct Answer:38,40

40

Correct Answer:287,290

290

Correct Answer:296,300

300

Correct Answer:1398,1400

1400

Correct Answer:1388,1390

1390

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.
Correct Answer: zeros, 0, zeroes, zero
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?
Correct answer: 4499.9999999999 kg
4500.008 kg
4984.2 kg
5050.50 kg
Correct answer: 5500.50 kg
Q3.
Round 345 678 to the nearest ten thousand.
Correct Answer: 350 000, 350000
Q4.
Round 15.0872 to 1 decimal place.
Correct Answer: 15.1
Q5.
Round each of the following to 2 significant figures.
Correct Answer:0.0108,0.011

0.011

Correct Answer:0.0121,0.012

0.012

Correct Answer:0.0103,0.010

0.010

Correct Answer:10.09987,10

10

Correct Answer:11.085,11

11

Correct Answer:11.85,12

12

Q6.
Which of the following do not give the same answer when rounded to 2 significant figures or truncated to 2 significant figures?
78 426
Correct answer: 458 500
Correct answer: 0.1297
0.010097
0.000204503