Key points
When it鈥檚 not necessary to give an exact value, numbers can be rounded. Rounding means making a number simpler but keeping its value close to what it is.
When rounding numbers the result is less accurate, but easier to use. For example, if there were 39,828 spectators at a music concert the headline in a newspaper report might say 40,000 fans attended the event.
Depending on the size of the numbers, numbers can be rounded up or down to the nearest:
- whole number
- ten
- hundred
- thousand
Rounding Numbers
There are steps which can be followed to decide whether a number should be rounded up or rounded down.
Identify the digitOne of the symbols of a number system, most commonly the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 in the column that you are rounding to. For example, if rounding to the nearest hundred then identify the digit in the hundreds place value column.
Leave the digit the same if the next digit is less than 5 (this is called rounding down)but increase it by 1 if the next digit is 5 or more (this is called rounding up)
Using a number lineA straight line on which numbers are marked at equal intervals. as a representation is a useful way of visualising whether a number is closer to one value or another.
When using values on a number line, marking the halfway point can help to identify whether to round up or down.
Examples
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A range of values
Sometimes you are given a rounded version of a number and need to explain what the original value was. In effect you need to work backwards.
Drawing a number line is a helpful representation to identify the minimum and maximum values that could have been used.
The number line should be increasing in the same sized step that the rounded value has been given to. (For example, if the rounded value is 70 to the nearest 10, then the number line should increase in steps of 10)
Examples
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Question
Which of these numbers when rounded to the nearest hundred give 11,600?
When rounded to the nearest hundred, 11,550 and 11,601 would give 11,600
11,669 is rounded to 11,700
11,701 is rounded to 11,700
Practise rounding whole numbers
Practise rounding whole numbers in this quiz.
Quiz
Real-world maths
Rounding whole numbers is used regularly in everyday life.The exact figure or value is not always needed initially, particularly if people are deciding whether they can afford a product or not.
When shopping people often round the value of items they are buying to the nearest 拢1 and add them together to make sure they don鈥檛 over-spend.
Newspapers and magazines may round the attendance at sporting events or festivals to the nearest thousand or ten thousand in their headlines, rather than printing the actual attendance. This makes it easier for the audience to read and remember.
Game - Divided Islands
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More on Rounding and estimating
Find out more by working through a topic
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