Rounding a number occurs in the following ways:
- Using the nearest 10, 100, 1000, or other power of ten.
- Using the nearest whole number.
- Using a given number of decimal places.
- Using a given number of significant figures.
Rounding to powers of ten
Rounding to powers of ten involves round large whole numbers to the nearest 10, 100, 1000, 10,000 etc.
For example, round 54,921 to the nearest 100.
- The number on the hundreds position is the digit which is used to round up
- In this example look to see if the lowest digit rounds up (in this case 1 does not) therefore the tens digit is the same and does not increase the hundreds digit
- Then check if the tens digits rounds up to the hundred (in this case 2 does not)
Therefore the solution is 54,900
Rounding to the nearest whole number
This rule is similar to rounding to the nearest power of ten.
For example, round 2.76 to the nearest whole number
- The first hundredth from the decimal is 6
- This round up the next tenth decimal from 7 to 8
- The tenth decimal of 8 would then round the whole number of 2 to 3.
Therefore the answer is 3
Rounding using a given number of decimal places
Again the rules of rounding up are used in this example
For example, round 4.75342113 to one decimal place
- Review thee digit in the first decimal place
- Write down the digit after this and look at the digit in the second decimal place
- If this digit is 5 or more then it is rounded up in the first decimal place
Therefore the answer is 4.8
Rounding to significant figures
The final example of number rounded is when a given number is rounded to significant figures.
A number which the first digit is not a zero – first significant figure (e.g. 4,582,573 the four in this example or 6 in 0.006457)
Digits which follow immediately after the first significant figure is known as the second, third, forth etc.
The forth significant figure in this example (4,582,573) is 2 and in this example (0.006457) is 7.