Final answer:
To calculate the total mass of the rocks, align the decimal points and add zeros as needed; the result is then rounded based on the least precise measurement. Significant figures play a key role in ensuring that the final answer reflects the precision of the initial measurements, and rounding is necessary when combining values with different levels of precision.
Step-by-step explanation:
When adding the masses of the rocks given as 3.56 grams, 1.742 grams, and 2.4 grams, you should align the decimal points and add zeros where necessary to keep the place values consistent. It's important to understand how to work with significant figures when combining measurements that have different levels of precision. When adding or subtracting data in scientific and mathematical contexts, the result should always be rounded to the same number of decimal places as the least precise measurement.
In the case of estimating the sum, you would round each number to the nearest place of the least precise measurement before adding. For example, if our least precise measurement was to the tenths place, we would estimate the masses as 3.6 grams, 1.7 grams, and 2.4 grams before summing, which would give an estimated total mass of 7.7 grams. This process of rounding and estimating helps to ensure that the final answer reflects the precision of the initial measurements.