Rounding to the nearest 10
Rounding is used to make numbers easier to calculate with, particularly when doing maths in your head. For example, if you went shopping, you might keep a rough running total of what you had spent to check if you had enough money when you got to the till.
When we round, we give a rough approximation of the number. So if I'd spent £18 shopping, I might say "about £20" - this is an example of rounding to the nearest 10.
Think about a number line from 20 to 30. The numbers 21, 22, ... 28, 29 all lie somewhere on that number line. To round any of these to the nearest 10, simply think about the position on that number line, and work out if it is closer to 20 or 30. So 24 would round to 20 to the nearest 10, because it is closer to 20 than 30, but 27 would round up to 30.
25 is right in the middle between 20 and 30. Although it is exactly halfway, by convention (that just means something we've all decided to do in a certain way), we always round up to the next 10. You might sometimes here the rule "5 or more rounds up".
To round without drawing a number line, first identify the tens digit. Next, work out the next 10 up. Finally, check the units digit to see if the number should stay (or round down) to its current tens digit, or round up to the next 10.
- IXL: Online questions with solutions.