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\ 10-Nov-2025 Bharat Arora Proof-8 Reader’s Sign _______________________ Date __________

EStiMAtiNg thE SuM

Sometimes we are not required to find the exact sum of numbers. An estimated sum
fulfills our purpose in these cases. We round off the numbers to find the estimated sum.
The estimated sum and the actual sum are different but are quite close to each other.

Example. Find the estimated sum to the nearest 100 of the following numbers.
a. 275 + 538 b. 1453 + 2107

Solution. a. H T O H T O
2 7 5 rounded 3 0 0
+ 5 3 8 rounded + 5 0 0

8 1 3 8 0 0

Actual sum Estimated sum

b. Th H T O Th H T O
1 4 5 3 rounded 1 5 0 0
+ 2 1 0 7 rounded + 2 1 0 0

3 5 6 0 3 6 0 0

Actual sum Estimated sum

Exercise 2B

1. Estimate each sum by rounding numbers to the nearest 10. Also find the actual sum.

a. 95 + 34 b. 273 + 158 c. 325 + 428 d. 4362 + 1537
e. 2431 + 2352 f. 1634 + 2158 g. 34902 + 41085 h. 24425 + 54351

2. Estimate each sum by rounding numbers to the nearest 100. Also find the actual sum.
a. 956 + 538 b. 289 + 765 c. 601 + 572 d. 9860 + 4522
e. 7014 + 6678 f. 45329 + 9324 g. 23482 + 48599 h. 21702 + 15096

AdditioN WoRd PRoBLEMS

Example 1. The population of City A is 25301; population of City B is 35701 and
population of City C is 29032. What is the total population of the three cities?

Solution. Population of City A = 2 5 3 0 1

Population of City B = 3 5 7 0 1
Population of City C = + 2 9 0 3 2
Total population = 9 0 0 3 4

The total population of the three cities is 90034.

30 Mathematics 4