Final answer:
To find the density, you divide the mass by the volume and round the result to the number of significant figures dictated by the measurements used. If the volume has three significant figures, your density should also be rounded to three significant figures. Arbitrary rounding without a valid reason is not scientifically acceptable.
Step-by-step explanation:
The density of a substance is calculated by dividing its mass by its volume. Let's say a mass of 37.46 g is divided by a volume of 12.7 cm³, resulting in a long decimal number on your calculator. To ensure the accuracy of your result in terms of significant figures, you should round it to the same number of significant figures as the measurement with the least number of significant figures.
For a mass measurement with four significant figures and a volume measurement with three significant figures, you would round your density calculation to three significant figures. Therefore, if your calculation result was 1.84847473737727, it should be rounded to 1.85 g/cm³ (assuming that the volume has three significant figures).
If you are aiming to round your result to a specific number like 1.3 for some reason, you should only do so if that level of precision is acceptable for your purposes, and you should clearly indicate that you have rounded the number for simplicity.
However, for scientific accuracy and integrity, you should not arbitrarily round numbers without a valid reason. To answer the student's question, Option A: Divide the mass by the volume and round the result to 1.3 is generally the correct method to determine density, but one should round according to the rules of significant figures as explained.