DISCLAIMER
This PDF was converted from a Word file. As a result, there may be formatting issues with the document.
To fix formatting issues, convert this PDF back into a Word document (turn on editing permissions if
needed) and edit the line spacing, text size and colour, etc, to your liking. It is recommended that the
practise questions and answers (see bottom of document) are on separate pages. You may also want to
delete this disclaimer and any other unwanted text in order to save ink if you decide to print this out.
Rounding and Estimation
Definition: Rounding is where you replace a number with another Key (text colour coding):
value for a simpler representation.
Green = Important Information
For example, say there are exactly 18,402 people going to watch a Blue = Methods/Instructions
football match. You don’t really need this much precision; 1 extra
person in a crowd of tens of thousands won’t make a difference. Red = Examples
Therefore, a much simpler way of representing the amount of people
who go to the match would be 18,000. How to do this will be explained later.
Definition: Estimation is where you roughly calculate the value of something to the required accuracy.
5.6(7.9−6.2)
For example, say you have the following problem to solve, . The decimal points in this
4.7
question make it very time-consuming to calculate, so we ideally want to round these numbers to the
nearest whole number. How to do this will be explained later.
Note: Exams do not allow estimation as a valid method of calculation unless specifically instructed to.
How to round numbers:
There are two ways to round a number – up or down. Rounding up will increase a number’s value and
rounding down will decrease a number’s value.
For example, take the number 9483. To round this number to the nearest 100 (this is essentially asking
“What is the closest value to this number that is a multiple of 100?”):
1. Locate the hundred’s digit and move one digit to the right, ending on the ten’s digit.
If the ten’s digit is 0, 1, 2, 3, or 4, we convert the specified digit and all digits to its right to 0 (don’t change
any other numbers). If this digit is 5, 6, 7, 8, or 9, we convert the specified digit and all digits to its right to
0 and add 1 to the hundred’s digit.
2. In the case of 9483, the ten’s digit is an 8. Therefore, we follow the process described above and
get the answer 9500.
Another example: Round 7482 to the nearest ten.
1. Locate the digit specified in the question, the ten’s digit in this case.
7482
This PDF was converted from a Word file. As a result, there may be formatting issues with the document.
To fix formatting issues, convert this PDF back into a Word document (turn on editing permissions if
needed) and edit the line spacing, text size and colour, etc, to your liking. It is recommended that the
practise questions and answers (see bottom of document) are on separate pages. You may also want to
delete this disclaimer and any other unwanted text in order to save ink if you decide to print this out.
Rounding and Estimation
Definition: Rounding is where you replace a number with another Key (text colour coding):
value for a simpler representation.
Green = Important Information
For example, say there are exactly 18,402 people going to watch a Blue = Methods/Instructions
football match. You don’t really need this much precision; 1 extra
person in a crowd of tens of thousands won’t make a difference. Red = Examples
Therefore, a much simpler way of representing the amount of people
who go to the match would be 18,000. How to do this will be explained later.
Definition: Estimation is where you roughly calculate the value of something to the required accuracy.
5.6(7.9−6.2)
For example, say you have the following problem to solve, . The decimal points in this
4.7
question make it very time-consuming to calculate, so we ideally want to round these numbers to the
nearest whole number. How to do this will be explained later.
Note: Exams do not allow estimation as a valid method of calculation unless specifically instructed to.
How to round numbers:
There are two ways to round a number – up or down. Rounding up will increase a number’s value and
rounding down will decrease a number’s value.
For example, take the number 9483. To round this number to the nearest 100 (this is essentially asking
“What is the closest value to this number that is a multiple of 100?”):
1. Locate the hundred’s digit and move one digit to the right, ending on the ten’s digit.
If the ten’s digit is 0, 1, 2, 3, or 4, we convert the specified digit and all digits to its right to 0 (don’t change
any other numbers). If this digit is 5, 6, 7, 8, or 9, we convert the specified digit and all digits to its right to
0 and add 1 to the hundred’s digit.
2. In the case of 9483, the ten’s digit is an 8. Therefore, we follow the process described above and
get the answer 9500.
Another example: Round 7482 to the nearest ten.
1. Locate the digit specified in the question, the ten’s digit in this case.
7482
