MathematicsClass 6Knowing Our Numbers
Estimation
Rounding off numbers to the nearest tens, hundreds, and thousands to find rough estimates.
Class 6 · MathematicsCBSE & ICSE
Definition
Estimation refers to finding a close approximation of a value for a purpose where an exact calculation is not needed. It is done by rounding off numbers to the nearest tens, hundreds, thousands, or higher place values.
Worked examples
1
Estimate 78 to the nearest tens: Since the units digit 8 is greater than or equal to 5, round up to 80.
2
Estimate 342 to the nearest hundreds: Since the tens digit 4 is less than 5, round down to 300.
3
Estimate the sum 458 + 639 by rounding to nearest hundreds: 500 + 600 = 1100.
Common mistakes
- • Looking at the wrong place value digit when deciding whether to round up or down.
- • Rounding down when the digit is 5 or more.
- • Changing the digits to the left of the rounding place instead of keeping them the same.