Page 34 - Math Skill - 4
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32 Maths
Estimation of Sum and Difference
For estimating the sum and difference, do as follows:
To estimate the sum of given numbers, we round off the given numbers and then find
the sum.
To estimate the difference of given numbers, we round off the given numbers and then
find their difference.
Let us learn through examples.
Let’s Attempt
Example 1: Estimate the sum of 84 and 91 to the nearest ten.
Solution: 84 rounded off to nearest ten = 80
91 rounded off to nearest ten = 90
Thus, estimated sum = 80 + 90 = 170
Example 2: Estimate the difference of 743 and 275 to the nearest hundred.
Solution: Rounding off 743 to nearest hundred, we get 700
Rounding off 275 to nearest hundred, we get 300
Thus, estimated difference = 700 – 300 = 400
Example 3: Estimate the sum of 3456 and 2341 to the nearest thousand.
Solution: 3456 rounded off to nearest thousand = 3000
2341 rounded off to nearest thousand = 2000
Thus, estimated sum = 3000 + 2000 = 5000
Exercise 2.8
1. Estimate the sum or difference to the nearest ten.
(a) 85 + 27 (b) 91 – 37 (c) 561 + 238
(d) 750 – 168 (e) 437 – 285 (f) 349 + 472
2. Estimate the sum or difference to the nearest hundred.
(a) 345 + 289 (b) 650 – 289 (c) 2130 + 3485
(d) 1789 – 685 (e) 10093 + 39279 (f) 24385 – 6243
3. Estimate the sum or difference to the nearest thousand.
(a) 28239 + 17432 (b) 62145 + 13849 (c) 23409 – 6197
(d) 56005 – 39266 (e) 2648 + 3947 (f) 34921 – 17169
