How is specific gravity calculated?

Specific gravity is a measure of the density of a substance compared to the density of water at a specific temperature, usually 4 degrees Celsius, where water is at its maximum density. It is calculated as the ratio of the density of the substance to the density of water.

The correct method involves taking the weight of a specific volume of the fluid and relating it to the weight of the same volume of water, which can lead to the correct determination of specific gravity. When you multiply the fluid weight by the specific gravity value, you’re effectively assessing how much heavier or lighter the fluid is compared to water for a specific volume. This approach allows for a direct comparison which defines specific gravity meaningfully.

This method is consistent with the concept that specific gravity is dimensionless, representing a ratio, rather than a direct measurement that involves mixing or manipulating the properties of volume and weight in other ways, as seen in the other options.