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Estimating to the nearest tens means rounding a number to the closest multiple of 10.
This makes calculations easier and faster, especially in mental math.
For Example:
Follow these simple steps:
Step I: Look at the ones digit (last digit of the number).
Step II: If the ones digit is 0, 1, 2, 3, or 4 β round DOWN
Step III: If the ones digit is 5, 6, 7, 8, or 9 β round UP
The numbers that are halfway or above are rounded off to the next 10 and the numbers that are less than halfway are rounded off to the existing 10.
For Example:
(i) 24 is closer to 20 (or less than halfway). So, it can be rounded down to 20.
(ii) 26 is closer to 30 (or above the halfway). So, it can be rounded up to 30.
(iii) 25 is closer to 30 (or at the halfway). So, it can be rounded up to 30.
In order to estimate to nearest tens, we follow the following procedure:
Step I: Obtain the number.
Step II: Examine the digit at ones place.
Step III: If the digit at ones place is less than 5, then replace the ones digit by 0 and keep the other digits as they are;
If the digit at ones place is 5 or greater than 5, then increase tens digit by 1 and replace the ones digit by 0.
The number so obtained is the number obtained by rounding off the given number to the nearest tens.
Now, let us consider some of the examples how to estimate to nearest tens.
1. Round off each of the following numbers to the nearest tens:
(i) 79
Ones or unit digit in 79 is 9, which is greater than 5.
So, we replace the ones digit by 0 and increase the tens digit by 1 to get the rounded off number.
Hence, rounded off number = 80.
(ii) 44
The given number is 44.
Its ones or unit digit is 4, which is less than 5. So, we replace the ones digit by 0 to get the rounded off number.
Hence, rounded off number = 40.
(iii) 758
The given number is 758.
Its ones or unit digit is 8, which is greater than 5. So, we replace the ones digit by 0 and increase the tens digit by 1 to get the rounded off number.
Hence, 758 is rounded off as 760 to the nearest tens.
(iv) 9009
The given number is 9009.
Its ones or unit digit is 9, which is greater than 5. So, we increase
the tens digit by 1 and replace the ones digit by 0 to get the rounded
off number.
Hence, rounded off number = 9010.
(v) 50001
The given number is 50001.
Its ones or unit digit is 1, which is less than 5. So, we replace the units digit by 0 to get the rounded off number.
Hence, rounded off number = 50000.
Note:
For estimating to the nearest 10, we look at the digit in the ones place. If it is 0, 1, 2, 3 or 4 we replace it by zero. If the digit in the ones place is 5, 6, 7, 8, or 9 we replace it by zero. If the digit in the ones place is 5, 6, 7, 8 or 9 we replace it by zero and increase the digit in the tens place by 1.
Choose the correct rounded answer and score points!
1. A shop sold 2047 apples. Estimate to the nearest tens.
Solution:
The given number is 2047.
Its ones or unit digit is 7, which is greater than 5. So, we replace the ones digit by 0 and increase the tens digit by 1 to get the rounded off number.
Hence, 2047 is rounded off as 2050 to the nearest tens.
Answer: 2050
2. A student scored 1262 marks. Estimate the score.
Solution:
The given number is 1262.
Its ones or unit digit is 2, which is less than 5. So, we replace the ones digit by 0 to get the rounded off number.
Hence, 1262 is rounded off as 1260 to the nearest tens.
Answer: 1260
3. There are 5488 books in a library. Estimate to nearest tens.
Solution:
The given number is 5488.
Its ones or unit digit is 8, which is greater than 5. So, we replace the ones digit by 0 and increase the tens digit by 1 to get the rounded off number.
Hence, 5488 is rounded off as 5490 to the nearest tens.
Answer: 5490
1. Round the Following Numbers to the Nearest Tens
(a) 41 β ___
(b) 86 β ___
(c) 29 β ___
(d) 274 β ___
(e) 565 β ___
(f) 912 β ___
(g) 2399 β ___
(h) 65753 β ___
β Answers
(a) 40
(b) 90
(c) 30
(d) 270
(e) 570
(f) 910
(g) 2400
(h) 65750
1. What is rounding to the nearest tens?
Answer:
It means simplifying a number to the closest multiple of 10.
2. When do you round up?
Answer:
When the ones digit is 5 or greater.
3. When do you round down?
Answer:
When the ones digit is less than 5.
4. Why is rounding useful?
Answer:
It helps in quick calculations and estimation in daily life.
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