Estimate Products
Estimating a product means finding a value that is close to the exact answer. This is useful when an exact calculation is not needed or when you want to check whether an answer is reasonable.
A simple method
- Look at the numbers carefully. Decide which factor is easiest to round.
- Round one or both factors to nearby numbers that are easier to multiply. Usually round to the nearest ten, hundred, or another friendly number.
- Multiply the rounded numbers. This gives an estimate.
- Compare with the exact product if you have it. The estimate should be close, not necessarily equal.
Example idea
If a problem has numbers like 48 × 19, you might round to 50 × 20. Then multiply the rounded numbers to get a quick estimate.
How to check your estimate
- Ask whether your answer is reasonable for the size of the original numbers.
- If both factors were rounded up, the estimate may be a bit larger than the exact answer.
- If one factor was rounded up and the other down, the estimate may stay very close.
Tips
- Keep the rounding consistent.
- Do not round so much that the estimate becomes too far from the original product.
- Use the estimate to spot mistakes in calculations.