Final answer:
Front-end rounding involves rounding numbers to the leftmost digit before adding; it is helpful for quick estimates but can lead to less accuracy. When working with decimals, results should be rounded to the least precise decimal place to maintain significance in the final calculation.
Step-by-step explanation:
Using front-end rounding to estimate sums involves rounding each number to the leftmost digit before adding them together. This method provides a quick estimation but remember, the more you round, the less accurate the estimate becomes. For non-scientific purposes, such an approximate value may be sufficient, but fine calculations, such as those in scientific work, require more precision.
For example, to estimate the sum of 456 and 789, you would round each number to the nearest hundred (450 and 800) because the leftmost digit is in the hundreds place. Your estimated sum would be 1250. When adding or subtracting numbers with decimals, you would round the results to the same number of decimal places as the number with the fewest decimal places. This is to ensure that the result is as accurate as possible without losing significant figures due to unnecessary rounding of intermediate answers.