📖Definition
We Round numbers to make them easier to understand and use.
It's something we do everyday without really thinking about it. Eg. when somebody asks how long it took to get to school you say '10 minutes' rather than '9 minutes 38 seconds'
Method
When rounding, you'll be told what to round to for example 'round to the nearest 100', 'round to 1 decimal place' or 'round to the nearest mm'.
So, once you know what you're rounding to, find that digit in the number you're rounding.
Let's look at an example:
Round 4.357m to the nearest centimetre.
So, we need to find the digit that represents centimetres.
100cm = 1m, so we need the digit in the 100ths place ie. the 5 after the decimal point.
Now we need to decide whether to round up or down. To do this, look to the digit to the RIGHT of the one we're rounding to.
If it's 5 or more we round UP.
If it's 4 or less, we round DOWN.
In this case, it's a 7 so we round the 5 UP to a 6.
And our answer is 4.36m
💡Tips/hints
Look carefully at what you're rounding to - as in the example above, it may be a different unit to the one the number is expressed in.
✏️Example
What is 23.45 to 1 decimal place?
✅Solution
1 decimal place is the first number after the point that is, the 4.
Now to decide whether to round up or down, look at the digit to the right of it.
It's a 5 so we round up.
So, to 1 decimal place, 23.45 = 23.5