New
New
Year 8

Rounding decimals to significant figures

I can round decimals to a required number of significant figures.

New
New
Year 8

Rounding decimals to significant figures

I can round decimals to a required number of significant figures.

Lesson details

Key learning points

  1. Numbers bigger than 1 with decimals places can be rounded to significant figures.
  2. When working with numbers smaller than one it is important to carefully identify the first significant figure.
  3. Once the first significant figure is identified you can find any significant figure.
  4. It is important to know when zeros are and are not significant.

Common misconception

Assuming all zero digits are not significant.

Designing questions that contain zero digits in a variety of positions.

Keywords

  • Significant figure - 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.

  • Round - To change a number into another number that is approximately the same value but is easier to work with. E.g. round 561 to the nearest 10 is 560.

Using MWB ask pupils to down decimals with a given number of decimal places and a particular digit in given significant figure position. E.g. Write down a decimal with 5 digits after the decimal point and 3 as the second significant figure.
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.
In the number 56 072, the 7 is the significant figure.
Correct Answer: fourth, 4th
Q2.
Select the numbers that have 3 as the third significant figure.
538.92
Correct answer: 723.91
Correct answer: 10 384
500 039
Correct answer: 503 090
Q3.
Select all the numbers which have zeros that are not needed to preserve the place value of other digits.
Correct answer: 700.00700
7007.007
Correct answer: 70 070.070
770 000
7 070 000.07
Q4.
Match each number to the correct statement.
Correct Answer:750,5 is the second significant figure

5 is the second significant figure

Correct Answer:10 756,5 is the fourth significant figure

5 is the fourth significant figure

Correct Answer:500 167,5 is the first significant figure

5 is the first significant figure

Correct Answer:1 000 567,5 is the fifth significant figure

5 is the fifth significant figure

Correct Answer:6 051 007,5 is the third significant figure

5 is the third significant figure

Q5.
Round 9452 to 2 significant figures.
Correct Answer: 9500
Q6.
Round 8096.564 to 3 significant figures.
Correct Answer: 8100

6 Questions

Q1.
The first figure is the first non-zero digit in a number.
Correct Answer: significant
Q2.
Match each number to the correct statement.
Correct Answer:0.05053,5 is the first significant figure

5 is the first significant figure

Correct Answer:0.25032,2 is the first significant figure

2 is the first significant figure

Correct Answer:0.004602,4 is the first significant figure

4 is the first significant figure

Correct Answer:7.0644,7 is the first significant figure

7 is the first significant figure

Correct Answer:0.0003945,3 is the first significant figure

3 is the first significant figure

Q3.
Round 0.00754 to 2 significant figures.
Correct Answer: 0.0075
Q4.
Round 0.006083 to 3 significant figures.
Correct Answer: 0.00608
Q5.
Round 0.0495 to 2 significant figures.
Correct Answer: 0.050
Q6.
Round 0.03098 to 3 significant figures.
Correct Answer: 0.0310