Approximation of Numbers - JSS2 Mathematics Lesson Note

Decimal Places:

Approximation by decimal places involves rounding a number to a specified number of decimal digits. Here's how it works:

Example 1: Approximate 

3.14159 to 2 decimal places.

Solution: The third decimal place is 1. Since it is less than 5, we round down. Therefore, 

3.14159 rounded to 2 decimal places is 3.14.

Example 2: Approximate 

27.896 to 1 decimal place.

Solution: The second decimal place is 9. Since it is 5 or greater, we round up. Therefore, 

27.896 rounded to 1 decimal place is 27.9.

Significant Figures:

Significant figures indicate the precision of a number. The rules are:

• All non-zero digits are significant.
• Zeros between non-zero digits are significant.
• Leading zeros (zeros to the left of the first non-zero digit) are not significant.
• Trailing zeros (zeros to the right of the last non-zero digit) in a number with a decimal point are significant.

Example 1: Determine the number of significant figures in 0.00345.

Solution: There are 3 significant figures.

Example 2: Determine the number of significant figures in 2300.

Solution: There are 2 significant figures (assuming it is 2.3×10/3).