# Round off numbers

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1. Slide
60 seconds
Understanding IGCSE Rounding
Rounding is a process of making a number simpler and easier to work with. When rounding, you look at the number to the right of the digit you want to round and decide whether to round up or down. In IGCSE, numbers ending in 5, 6, 7, 8 & 9 are rounded up, while numbers ending in 0, 1, 2, 3 & 4 are rounded down.
2. Slide
60 seconds
IGCSE Rounding
Rounding: The process of reducing the number of digits in a number while preserving its value as much as possible.
Rounding Numbers to the Nearest Ten: Finding the nearest ten by looking at the digit in the ones place.
Rounding Numbers to the Nearest Hundred: Finding the nearest hundred by looking at the digit in the tens place.
3. Slide
60 seconds
Did you know?
In the IGCSE curriculum, when rounding a number, you should always round up if the last digit is 5 or more. In the IGCSE curriculum, when rounding a number to the nearest whole number, you should look at the digit to the right of the decimal point. In the IGCSE curriculum, when rounding a number to the nearest 10, you should look at the digit to the right of the hundreds place.
4. Word cloud
120 seconds
Name a method for rounding off numbers?
5. Slide
60 seconds
Rounding off Numbers
Rounding off numbers means adjusting the number to make it simpler and easier to work with. For example, if you have a number like 6.48, you can round it off to 6.5. Rounding off numbers can make it easier to add, subtract, multiply, and divide.
6. Slide
60 seconds
Rounding off numbers
Rounding: Rounding is the process of replacing a number with one that is approximately equal, but has fewer digits.
Rounding to the Nearest Ten: To round to the nearest ten, look at the digit in the ones place. If it is 5 or more, round up. If it is 4 or less, round down.
Rounding to the Nearest Hundred: To round to the nearest hundred, look at the digit in the tens place. If it is 5 or more, round up. If it is 4 or less, round down.
7. Slide
60 seconds
Did you know?
Numbers can be rounded off to the nearest thousands place by first finding the thousands place, then looking at the number after it. If it is 5 or more, add 1 to the thousands place. If it is less than 5, leave the thousands place as is. The word 'round' is derived from the latin word 'rotundus', which means 'round' or 'circular'. In some cultures, the number 8 is considered a lucky number because it is associated with wealth and abundance due to its shape resembling the ancient Chinese symbol for infinity.
8. Open question
300 seconds
What is the difference between rounding off a number to 1 decimal place and 1 significant figure?
9. Open question
300 seconds
Can you think of a situation where it is important to round off numbers to 3 decimal places?
10. Open question
300 seconds
Can you explain why it is important to understand how to round off numbers?
11. Open question
300 seconds
What strategies could you use to help you remember how to round off numbers?
12. Drawings
450 seconds
Brain break: Draw a funny-faced whale blowing bubbles from its blowhole
13. Drawings
1260 seconds
Clues
In pairs: Select one task
Question: Jill and Joe need to round off the number 639.45 to the nearest whole number. What is the answer?
Remember, rounding goes up if the number after the decimal is 5 or more. Look at the number to the right of the decimal point. What is it? Think about what would happen if you add 0.5 to the number before the decimal point.
A: Work with a partner to explain how to round off 639.45 to the nearest whole number through a drawing. B: Round off 624.98 to the nearest whole number and explain your solution through a drawing.
14. Poll
60 seconds
What is the rounded value of 3.1415 to two decimal places?
• 3.15
• 3.14
• 3.13
15. Poll
60 seconds
If you round off 63 to the nearest ten, what is the result?
• 60
• 65
• 70
16. Poll
60 seconds
What is the rounded value of 8.75 to one decimal place?
• 8.7
• 9
• 8.8
17. Poll
60 seconds
If you round off -2.83 to the nearest whole number, what is the result?
• -1
• -3
• -2
18. Open question
180 seconds
Work together in pairs: What is the rule for rounding off a number to the nearest 10?
19. Word cloud
120 seconds
Name a method for rounding off numbers?
20. Slide
60 seconds
Rounding off Numbers
Rounding off numbers means adjusting the number to make it simpler and easier to work with. For example, if you have a number like 6.48, you can round it off to 6.5. Rounding off numbers can make it easier to add, subtract, multiply, and divide.
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