Page 1 - Lesson Note

Subject — Mathematics

Chapter 2 - OPERATION ON LARGE NUMBERS

Sub-topic 10 : Estimating Operations

Introduction — We use estimation to make out calculation easier.

**Estimation means “Rounding Off’

Estimating Sum: We round off the addends and then find out the sum.
Example 1: Find the sum of 2345 and 9872 after rounding off them to the
nearest 100.
Solution:
Step 1: round off 2345 to the nearest 100.
23452300
Step 2: round off 9872 to the nearest 100.
9872 9900
Step 3: add the rounded off value.
2300 + 9900 = 12200
Estimating Difference: We round off the minuend and subtrahend, then
subtract the numbers.
Example 1: Find the difference between 32908 and 12453 after rounding off
them to the nearest 1000.
Solution:
Step 1: round off 32908 to the nearest 1000.
32908 33000
Step 2: round off 12453 to the nearest 1000.
12453 12000
Step 3: subtract the rounded off value.
33000 — 12000 = 21000
Estimating Product: We round off the multiplier and the multiplicand, then

multiply the numbers.
Example 1: Estimate the product of 543 and 876.
Solution:

**Here, we have to round off both the numbers to nearest 100 as it will be
easier to get the product.
Step 1: round off 543 to the nearest 100.
543- 500
Step 2: round off 876 to the nearest 100.
876 900
Step 3: multiply the rounded off numbers
500 X 900 = 450000