Once youve decided where to round a number you need

Once you’ve decided where to round a number, you need to look at the
digit immediately after where you want to round. You round up if this
digit is 5 or more, and round down otherwise. When you round a number,
you should state how it’s been rounded, in brackets after the rounded
number, as illustrated in the next example.
Notice the ‘play button’ icon next to the following example. It indicates
that the example has an associated tutorial clip – a short video in which a
tutor works through the example and explains it. You can watch the clip,
which is available on the module website, instead of reading through the
worked example. Many other examples in the module have tutorial clips,
indicated by the same icon.
11

Unit 1 Algebra
Example 2
Rounding numbers
Round the following numbers as indicated.
(a) 0.0238 to three decimal places
(b) 50 629 to three significant figures
(c) 0.002 958 2 to two significant figures
Solution
Activity 2 Rounding numbers
Round the following numbers as indicated.
(a) 41.394 to one decimal place
(b) 22.325 to three significant figures
(c) 80 014 to three significant figures
(d) 0.056 97 to two significant figures
(e) 0.006 996 to three significant figures
(f) 56 311 to the nearest hundred
(g) 72 991 to the nearest hundred
12

1 Numbers
The use of the digit 0 to indicate an empty place in the representation
A Babylonian clay tablet
from around 1700 BC
of a number seems essential nowadays. For example, the digit 0 in
3802 distinguishes it from 382. However, many civilisations managed
to use place-value representations of numbers for hundreds of years
with no symbol for the digit zero. Instead, they distinguished numbers
by their context. Evidence from surviving clay tablets shows that the
Babylonians used place-value representations of numbers from at least
2100 BC, and used a place-holder for zero from around 600 BC.
When you need to round a negative number, you should round the part
after the minus sign in the same way that you would round a positive
number. For example,
− 0 . 25 = − 0 . 3 (to 1 d.p.).
When you’re rounding an answer obtained from your calculator, it’s often
useful to write down a more precise version of the answer before you round
it. You can do this by using the ‘ . . . ’ symbol, like this:
9 . 869 604 40 . . . = 9 . 87 (to 2 d.p.).