Estimation of the Numbers
A reasonable guess of the actual value is called an estimate.A quick, rough estimate of the result of number operations can be done by rounding off the numbers is involved.Thus, estimation is a rough calculation of value. We use estimations when we have to deal with large numbers and to do the quick calculations.
Rules of Estimation
1)Estimating numbers to the nearest tens is done by rounding off numbers 1, 2, 3 and 4 to 0 and number 6, 7, 8, 9 to 10.
2) Estimating numbers to the nearest hundreds is done by rounding off numbers 1 to 49 to 0 and numbers 51 to 99 to 100.
3) Estimating numbers to the nearest thousands is done by rounding off numbers 1 to 499 to 0 and the numbers 501 to 999 to 1000.
Estimation involves approximating a quantity to an accuracy required. We can apply the above rules depending on the accuracy required.
Here 38 lie between 30 and 40
Secondly, we will see if it is 5 or higher.
Yes it is higher than 5 i.e. 38
Thus the number 738 is rounded off to 740.
Now we have to check for tens place. If it is greater than 50 then we will round it off to the upper side and if it is less than 50 then we will round it off on the lower side.
It is 67, which is greater than 50 and is closer to 900.
Thus 867 is rounded off to 900
Example 3: Round off the number 7690 nearest to thousands.
Solution:
It lies between 7000 and 8000
And is closer to 8000
Thus 7690 is rounded off to 8000.
To estimate sum or difference
Example 1 : Estimate: 3,210 + 12,884
Solution
3,210 will be rounded off to 3000.
12,884 will be rounded off to 13000.
3000+ 13000
Estimated solution = 16000
Actual solution = 3,210 + 12 884
= 16,094
To estimate products
Exanple 2 : Estimate: 73 × 18
Solution
73 will be rounded off to 70
18 will be rounded off to 20
70 × 20
Estimated solution = 1400
Actual solution = 73 × 18
= 1314