Number- Rounding numbers ( 2, 3 and 4 digit numbers)
Topic: Rounding NumbersRounding means making a number simpler but keeping its value close to what it was. Rounding two(2) digit numbers to the nearest ten The rules for rounding numbers: Step 1 Decide which is the last digit to keep Step 2 Leave it the same if the next digit is less than 5 (this is called rounding down) Step 3 But increase it by 1 if the next digit is 5 or more (this is called rounding up)
Example: Round 54 to the nearest 10
- We want to keep the “5” (it is in the 10s position)
- The next digit is “4” which is less than 5, so no change is needed to “5”
Answer: 50
(54 gets “rounded down”)
Example: Round 78 to the nearest 10
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We want to keep the "7" -
The next digit is "8" which is 5 or more, so increase the "7" by 1 to "8"
Answer: 80 (78 gets "rounded up") Watch the video below to learn more about rounding numbers
Rounding three(3) digit numbers We follow the same basic rule of rounding up when the number in focus is equal to or greater than 5 and rounding down otherwise, we learnt previously except now we look at the tens place number. When rounding to the nearest hundred, look at the TENS DIGIT of the number.
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If that digit is 0, 1, 2, 3, or 4, you will round down to the previous hundred. -
If that digit is 5, 6, 7, 8, or 9, you will round up to the next hundred.
Example: 1. 638 ≈ ? The tens digit is 3, so round down: 638 ≈ 500 2. 976 ≈ ? The tens digit is 7, so round up: 976 ≈ 1000 Rounding four(4) digit numbers By now you have the strongest foundation in knowledge of rounding numbers, the last set of numbers we look at rounding are four digit numbers. Can you guess what place value we will be looking at to determine if we round up or down? If you said the hundredth you are correct!! Example: 1. 4687 rounds up to 5000 because the hundreds digit is 6. 2. 8296 rounds down to 8000 because the hundreds digit is 2. 3. 11583 rounds up to 12000 because the hundreds digit is a 5. Watch the video below
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