Why do we need to round numbers?
- because we don't use one cent pieces, so $5.73 needs to round to the nearest multiple of 5 cents
- to estimate or think about numbers in an easier way, e.g. 567 + 298 seems difficult, but we can estimate an answer very easily when we round these numbers to 570 + 300
When you round numbers, use the floor - ceiling method: Think about the two possibilities and place these on a number line:
E.g. Round 2.31 to the nearest one/whole number:
2.31 is closer to the floor, so it rounds down.
You can also remember how to round numbers using the rounding mountain or number line:
Extra tips
When you have to round a number, what should your first question be?
What do I need to round the number to? Is it the nearest whole number, or ten, or hundred, or thousand, or to a decimal place?
What do I need to round the number to? Is it the nearest whole number, or ten, or hundred, or thousand, or to a decimal place?
Remember, if you need to round to the nearest ten, your answer must be able to be counted by tens, e.g. 1,050 - 1,060 - 1,070 - 1,080 - 1,090 - 2,000 - 2,010 and so on. Your answer cannot be 1055 because it's not a multiple of 10.
If you need to round to the nearest hundred, it must be able to be counted by 100s, e.g. 5,200 - 5,300 - 5,400 - 5,500 - 5,600 - 5,700 - 5,800 - 5,900 - 6,000 - 6,100. Not, 6,520, that can't be the nearest 100!
Remember to use the next lowest place value to help figure out whether you need to round up or round down: e.g. round 7,080 to the nearest 100. Well it's either going to be 7,000 or 7,100. But 7,080 is closest to 7,100 because the 8 in the tens rounds up. 0, 1, 2, 3 and 4 are all lower numbers, 5, 6, 7, 8 and 9 are all higher numbers.
Practice makes Perfect
- Rounding legend: Read the information on this site, then try out the questions at the bottom.
- Play darts: For this game, make sure you click on the 'input answers' (right hand side). Read these tips to become a master darts-man or darts-lady:
- Find the rounding treasure: Search the island for treasure as a rounding pirate.
- Soccer Decimal Rounding Shootout: Read these tips to become a decimal soccer champion: Make sure you use the mouse-pad for the clicks to shoot for goals. Remember, whole numbers are 5, 809 or 74, not 74.5, 67.29 or 89.54.
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