Estimation
Estimate sums, differences, and products by rounding first.
Objective
Estimate sums, differences, and products by rounding first.
What it means
Estimation gives a quick, approximate answer by rounding numbers before computing.
See it
Use this model while you read. Move it around to see what the math is doing.
Key terms
- Estimate
- An approximate answer found using rounded numbers.
- Front-end estimation
- Using only the leading digits of numbers to estimate.
Rules to remember
- Round each number to the same place value before computing.
- Estimation checks whether an exact answer is reasonable.
Step by step
- 1Round each numberRound each value to a convenient place (often the highest place).
- 2Compute with rounded valuesAdd, subtract, or multiply the rounded numbers.
Common mistakes
- Rounding numbers to different places, which makes estimates unreliable.
- Treating the estimate as if it were the exact answer.
Tips
- Use estimation to check that an exact calculator answer is in the right ballpark.