A substance has density 49.3 lb/ft^3; water density is 62.4 lb/ft^3. What is its specific gravity (SG) to two decimals?

A substance has density 49.3 lb/ft^3; water density is 62.4 lb/ft^3. What is its specific gravity (SG) to two decimals?

• A. 0.75
• B. 0.79
• C. 0.83
• D. 0.81

Answer: (B)

Specific gravity compares how dense a material is to water, and it’s a pure number since it’s a ratio of densities with units canceling out. Compute SG = density of substance ÷ density of water = 49.3 ÷ 62.4 ≈ 0.789, which rounds to 0.79. Since SG is less than 1, the substance is lighter than water and would float.

Specific gravity compares how dense a material is to water, and it’s a pure number since it’s a ratio of densities with units canceling out.

Compute SG = density of substance ÷ density of water = 49.3 ÷ 62.4 ≈ 0.789, which rounds to 0.79.

Since SG is less than 1, the substance is lighter than water and would float.