At the end of the lesson, students should be able to:
Numbers can also be approximated to a given number of significant figures (sf). We often use significant figures (sf) when we want to approximate a number with a lot of digits in it.
In the number 63.42 the 6 is the most significant figure as it has a value of 60. In contrast, the 2 is the least significant as it only has a value of 2 hundredths.
The steps taken to round a number to a given number of significant figures (sf) are very similar to those used for rounding to a given number of decimal places;
Write 0.0023 to 1sf.
In example, only two numbers have any significance (ie the 2 and the 3). The 2 is the most significant so we start our counting from the first non- zero digit. Observe that the next digit after 2 is 3 which less than 5. We therefore run down to get 0.0023.
Therefore 0.0023 is written as 0.002 to 1 sf.
Write 69.28 to 3 sf.
The three most significant numbers are 6, 9 and 2. However the fourth number needs to be considered to see whether the third number is to be rounded up or down. The fourth number is 8, therefore we round up to get 69.3
Therefore 69.28 is written as 69.3 to 3 sf.
Write 48599 to 1 sf.
The most significant number is 4 and the next number is 8. We round it up and the rest of the numbers become zeroes.
Therefore 48599 is written as 50000 to 1 sf.
Unit 9 lesson 3: Exercise 1
Write the following to the number of significant figures written in the brackets.
Unit 9 lesson 3: Exercise 2
Round each of the following to the number of significant figures (sf) indicated.