Unit 2 Section 1 : Place Value
In this section we will look at how we round numbers to a given accuracy.
We need to remind ourselves about the idea of place value in any particular number.
The "4" in the number above is actually worth 40000, because the place value of its position is tenthousand (10000).
Example Question 1
Work out the value of the "6" in each of the numbers below, then click
to see whether you are correct.
(a) 167
(b) 2006
(c) 6423
Rounding
There are times in Mathematics where we don't want to give all the detail of a number, so we round it to a given accuracy.
Think about the number 7451. We want to write this number to the "nearest ten".
The two "nearest tens" to 7451 are 7450 (below) and 7460 (above). The diagram below shows this:
We can easily see now that 7450 is the "nearest ten", so 7451 to the nearest 10 is 7450.

Now we want to write 7451 to the "nearest hundred".
Look at this diagram which shows the "nearest hundreds" to 7451:
We can see that 7451 to the nearest 100 is 7500.

Finally, we want to write 7451 to the "nearest thousand".
The "nearest thousands" to 7451 are 7000 and 8000, as shown below:
We can see that 7451 to the nearest 1000 is 7000.

Note
If a number is exactly halfway between two "nearest values", we always round up to the higher value.
For example, imagine rounding 350 to the nearest 100.
The diagram shows that 350 is exactly halfway between 300 and 400:
The "5" always rounds up, so 350 to the nearest 100 is 400.

Example Question 2
Work out the answers to the questions below, then click
to see whether you are correct.
(a) What is 2716 to the nearest 10?
(b) What is 2716 to the nearest 100?
(c) What is 2716 to the nearest 1000?
Exercises
Work out the answers to the questions below and fill in the boxes. Click on the
button to find out whether you have answered correctly. If you are right
then will appear and you should move on to the next
question. If appears then your answer is wrong. Click
on to clear your original answer and have another go.
If you can't work out the right answer then click on
to see
the answer.
You have now completed Unit 2 Section 1
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Produced by A.J.Reynolds January 2001