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Estimation is used to find a value that is close to the exact value of a product. This can be done by rounding the factors in the product to the greatest place value — the first non-zero digit on the left in a number. For example, consider the product of two decimal numbers. 35.92 * 0.014 Estimating this product can be done in two steps.
Next, make all digits to the right of the greatest place value zero. For 35.92, the digit to the right of the greatest place value is 5. For 0.014, the digit to the right of the greatest place value is 4.
| Estimate 35. 92 * 0.014 | ||
|---|---|---|
| Factor | Greatest Place Value | Digit to the Right |
| 3 5.92 | Tens | 5 |
| 0.01 4 | Hundredths | 4 |
The first factor will be rounded to the nearest ten. Since 5 is greater than or equal to 5, add 1 to the number in the rounded place 3. All place values to the right of 3 are replaced with zeros. 35.92 ≈ 40.00 (or 40) Similarly, for 0.014, the digit to the right of the greatest place value is 4. This is less than 5, so 1 remains the same and all place values to the right of 1 have a value of zero. 0.014 ≈ 0.010 (or 0.01) The numbers have now been rounded to their greatest place values. The procedure is visualized in the following applet.
